My wife and I have ATT smartphones in the US. We are going to live in Cuenca for a year. We want to keep our numbers and our phones. ATT said it was easy to port a US cell number over to an Ecuadorian cell provider. I am skeptical. Is this true?
Has anyone else been in the same situation and found a solution?
I have AT&T.
For technological reasons, I think it is impossible to port your number to the Ecuadorian system. The primary reason is that USA uses a 10 digit phone number, Ecuador uses 9.
But you can use AT&T in Ecuador, if you wish. But be careful, doing so can rack up $1000s per month if you just wing it and use roaming.
AT&T's roaming data is $2 per MB, and it is easy to use 200+ MB per week (so $800 or more per month!)
So follow AT&T's international instructions exactly!
I have two experiences using AT&T in Ecuador. In March 2017, I set up the AT&T Global Passport option on my lines before leaving Ohio. For 30 days, you get a 1GB limited plan for $60 per month.
 The problem was that AT&T didn't work very well in Ecuador in 2017. My AT&T data service was very spotty, most received calls went straight to voice mail, 2G data, etc. Quite frustrating. Not worth the $60. But it could be improved since then.
In April 2018, I tried the AT&T international day pass. For 24 hours and $10, on AT&T you get a free pass, unlimited texts and calls. The catch is: you have to put your phone in airplane mode and only use wifi when you Don't want to be charged by AT&T. If you Forget to do this, your plan will cost over $300 per month!
My experience with the AT&T international day pass in 2018 was quite good with service in Ecuador. I never had problems connecting. I decided only to use it so I could contact my elderly family in the USA who can't figure out WhatsApp and Skype. I used it in 5 days in 30. But I also bought a Ecuadorian Movistar prepago SIM on my second day in Ecuador. Now I have an Ecuadorian cell number. This is to your financial advantage, and not a big hassle.
My 9 step-by-step money saving advice for phones
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1 Get the AT&T international day pass on your lines before you travel.
2 Get an *Unlocked* Dual SIM smartphone in the USA before leaving.
3. Make sure your AT&T SIM works in your unlocked phone before you leave the USA
4. Your first morning in Ecuador, go to a Claro or Movistar store (who use the same GSM technology as AT&T) and get a SIM chip prepago. CNET will not work with AT&T phones.
5. Load the SIM chip with $10-$15 (that should last about a month)
6. Movistar has a cheap $3 weekly prepay subscription plan "Ahora 300 MB para navegar. 20 Min. Chat whatsapp gratis. 20 SMS". Claro has a  competitive paquete plan, also for $3: 200 Megas
Minutos Ilimitados, SMS Ilimitados Multidestino, Redes Sociales Whatsapp Gratis, 70 megas Facebook" ...Or choose whatever fits your budget.
7. After you test out your Ecuadorian SIM and everything is ok, turn off your AT&T SIM until you need it.
8. Tell all your contacts your new number.
9. By using WhatsApp and Wifi to chat with your US contacts, you probably won't use more that 300 MB per week. I run an online business and need to stay in touch with clients, and 300 MB was just fine.
In the end, i used $15 on MoviStar in April 2018. I used $50 on AT&T day pass, plus my regular AT&T plan.
When I relocate to Ecuador in October, I will drop AT&T after my first 30 days, and rely on Skype, WhatsApp, Google Voice, and MoviStar prepago. It will be easy and painless