I am on t mobile i use to have a HTC desire hd i sent that off for repairs and they sent me back a Samsung s2?

Which i had for five months then that went wrong sent it off for repairs and it came back with a dirty update so,they sent me another with a dirty update. So the women at t mobile said she would call me Monday at half twelve (this was on a Friday) i said fine i sent the old Samsung s2 back Monday at 1pm i didn't receive a phone call i rang back at four and one bloke from t mobile said you will have a call before the day is out i have emailed her so she knows she will ring you at five i waited till half six and still no call i rang back again and a women said the same thing i never receive a phone call i rang back this morning and now they are saying they still have not received the phones so they can't process the current Samsung s2 for an exchange till that one has come back and its a neXT day delivery could i cancel contract under any sounds or what could i ask for for inconvenience some one help me im banging my head against a brick wall yet again with t mobile

Thank you