Question on T-mobile phone issues on my Mytouch3g slide and contract?

[passionLoverrr<33]

for my birthday a few months ago i got the mytouch3g slide in black. it was the second day it was released so we payed more for what its worth now..obviously. the black was the first made of the series and theres deffinatly a few minor issues with it. one issue got so bad it eventually blacked out the screen to my phone and i took it in and had it replaced since its under a year ive owned it, i guess some kind of warentee they offer. my new one which ive only owned for about 4 months is having the same problem minus the black screen.. freezing after ive removed battery and turned off and on a few times and theres a huge problem with my onscreen keyboards not working which happened the same way with my last one. im completly unhappy with this and my dad doesnt like having to replace it..again. is there anyway i could exchange it for another phone of equal or less value if i take it into the store?