hello i bought an iphone 3g from a friend that used at&t but i have tmobile.
ok so i bought an i-smartphone sim and i put it in the phone correctly with my t-mobile sim..
i got signal bars and the t-mobile name next to the signal
ok heres the problem
i cant recieve calls they go straight to voicemail.
i call make calls however
i cant recieve text all the time..the come when they want
but i can send text and people get them instantly
im confused do i need to jail break the phone idk can someone help

Edit: ok..now when i call 611..ok..i get all the text i was supposed to get and i can get an incoming call while on the phone with 611..its like calling makes it connect to tmobile network somehow..and like 1 min after i and the call i still get text i test it by sending one to my own number idk whats worng plz help