phone says i cant connect to itunes, what do i do?

i hvae tried everything that apple suggests on their page aboput this, but when i try to do an in app purchase it says that i cannt connect to itunes. and wont let me buy it, its getting really annoying, ive had no problem with it before, but i recently got a new iphone and thats when it started to occur, any suggestions on what to do?