Panama is a "Simple Choice" country. You should have data service, if you are on a "Simple Choice" postpaid plan.
There is nothing wrong with trying to manually select a different carrier.
You can also try this:
1) set your APN to epc.tmobile.com
2) make sure that the IP mode is set to IPv4, not IPv6.
You can call T-Mobile direct international support line at +1-505-998-3793. It's a free call from your T-Mobile phone.