great phone great phone much to do

finally got it on christmas and my aunt thought i had at&t not tmobile so i put my sim card in and asked for a code i thought it was the code i set for the phone well i tried it and it said phone freeze, well i called at&t and they gave me the unlock code but by this time it was already too late, called samsung they said i could send it back to them and they could send it back but it would take up to a month... well i looked around here tried everything i could every code and boom now it's reading the tmobile card make calls recieve calls mms everythin internet all goood but when i check the lock status on the phone it still says its locked, and now the service bars go from 5 - 0 very very fast is that a problem that comes with unlocking the samsung impression to tmobile?

its samsung sgh-a877