My friend and I flew to Portugal through a popular airline. The red flags began months before we took off.

• My friend and I booked the Portuguese airline TAP Air Portugal to fly to and around Portugal.
• Months before we flew, we were notified our return flight to the US had been pushed back a full day.
• Later, we were bumped from an overbooked flight and another was canceled.

In November, my friend and I began booking a March trip to Portugal.

We selected our hotels and then moved on to flights.

While comparing prices, we found TAP Air Portugal, the country's national airline, had the most affordable nonstop flights, both from the US to Lisbon and from Lisbon to Madeira, a Portuguese island 600 miles into the Atlantic Ocean.

We each paid $565 roundtrip to fly from New York City to Lisbon, and $171 roundtrip to fly from Lisbon to Madeira.

Normally, I'm wary of low-cost flights from and within the US — I believe you always pay for something, be it a less-than-stellar flight experience or hidden fees.

However, TAP's flight costs seemed somewhat comparable to ones from other airlines so we didn't feel the need to research the airline too deeply. I've also flown other national airlines before — like Turkish Airlines, Air France, Icelandair — without a hitch. I assumed this would be the same.

We experienced our first red flag months before we flew, and our experience only got worse from there.

Our return flight changed 2 months in advance

In January, two months before our flight, we received an email stating that our itinerary had been changed.

Our return flight, from Lisbon to New York, was delayed 24 hours, with our flight now leaving on Friday, March 28, instead of Thursday, March 27.

We weren't given an explanation as to why. TAP Air Portugal did not respond to Business Insider's request for comment.

We had planned to fly on Thursday to save money. Staying an extra day would cost us around $200 for the hotel alone, plus other expenses, like dining out for the day (probably another $100).

Still, we decided to make the most of it. We accepted our new flight, budgeted for an extra day, and booked another hotel.

We planned to use the extra time in Lisbon to do a quick day trip to Sintra, a resort town about an hour away by train from Lisbon.

Although it wasn't the end of the world for us to stay longer, this would've been a huge inconvenience if either of us had a tighter budget or needed to be back in the States sooner.

Flying to and from Madeira didn't go as planned, either

Four days after we landed and explored Lisbon, it was time for us to fly to Madeira. Our flight was set to land on Wednesday afternoon.

We arrived at Lisbon's Humberto Delgado Airport almost three hours early. Once we checked in, we learned the flight was overbooked, and we didn't have assigned seats.

We joined a crowd of about a dozen people who were at the check-in desk looking to book new flights.

A TAP Air representative gave us two new seats for a flight five hours later, meaning we'd land at midnight and get only a few hours of sleep before our 5:30 a.m. hike the next morning.

He gave us $250 flight vouchers as well as meal and snack vouchers. We took them and played cards to pass the time until our next flight.

It was around 1 a.m. by the time we got to our Madeira hotel.

Soon, we were surprised with another flight cancellation

The next day, around 4 p.m., we got an email notifying us that our return flight to Lisbon in two days was canceled.

A few hours after receiving that message, we were notified that we had been automatically booked for a new, 9 p.m. flight on the day we planned to leave — a full 12 hours later than our original one.

Frustrated, my friend booked us on an earlier Ryanair flight back to Lisbon instead, which cost $113 each. Once again, we changed plans and unexpectedly spent more money.

Instead of going to Sintra, as we planned the first time our flights were altered, we looked for more things to do in Madeira because we'd be back in Lisbon later.

We booked a morning sunset excursion (with a 5:15 a.m. pickup time) to still feel like we did some exploring.

We didn't find TAP's website or customer service to be very helpful, either

After this flight cancellation, we were eligible for a refund, according to TAP Air's terms and conditions, because our flight was more than five hours delayed and we weren't taking a replacement flight through the airline.

There was just one problem: We weren't able to access the refund through the airline's website. I watched my friend input all her information, land on a confirmation page, hit "request refunds," and be prompted to restart the process again.

When she tried to file an online complaint, the message wouldn't go through. Instead, she was met with: "Your request was not sent successfully!" Because my friend bought both of our Madeira tickets, I tried inputting her information on my phone, with the same results.

Once we landed in Lisbon, we had about 24 hours until our flight home. We saw it as an opportunity to slow down after all the travel mishaps, spending the last few hours unwinding in our hotel.

When we arrived at the Lisbon airport for our flight back to New York City, we stopped by the TAP customer-service desk.

My friend took screen recordings of her trying to use the website and showed them to the representative. She was told by TAP Air's customer service that she could only request refunds on the website or over the phone.

"But the website doesn't work," my friend said.

"You have to use the website," the rep said.

While waiting to board our flight, I Googled other reviews of the airline. Reddit users lamented the customer service in particular, some saying it could take months to hear back. (One user said it took over three years).

We gave up on trying to get a refund through TAP Air. Weeks later, my friend is waiting to hear back on a credit-card chargeback she filed shortly after we landed.

We'd pay more for a different airline next time

Ultimately, we ended up paying way more than we budgeted for, both in money and time.

All in all, we each spent $113 for the new flights, $125 for the hotel, plus a little over $100 for dinner, breakfast, and lunch combined. Nearly $400 extra.

The problem wasn't that we had a canceled flight or got overbooked — it happens and is always something I'm mentally prepared for.

It's that we ticked off multiple unlucky flight experiences, all in one week. Next time, I'd definitely pay the extra $100 or $200 for a flight from an airline I've had better experiences with for an international flight, like Delta or United. I'd also stick to Ryanair or easyJet for shorter flights because I've at least had decent experiences with both.

Even with the free voucher, I wouldn't book TAP Air again. Or if I did, I would prepare to be disappointed and adjust my trip, over and over again.