I do not agree what you said, by two different reasons:
1.- The second phone was working normally with DIGICEL Trinidad, until the phone make a software up-date. Then for a three or four weeks the phone was able to communicate.
2.- If the problem were the band frecuency, it should be same problem all time, and it is not what happen.
I am able to make or receive one call before block, it means the phone is able to send and receive information, then the phone was connected.
DIGICEL Trinidad and Tobago use: GSM 850 and 1900, at least the phone should connect by GSM, if no possible to use UMTS or LTE.
Sorry, but I think the problem is different and not the local band frecuency.
Regards
Luis Possamay