bad service received very unhappy

I bought a blackberry z3 in January had a data problems spoke to the sales person she said 4to6weeks I said it's fine will just use airtime not long after that had problems with the apps closing on its own then finally the battery started heating up so I sent it in the phone was working I waited a month and a half the phone came back not working at all they sent the phone back to mtn so I can get a new phone its two weeks still nothing so I went to the store and they told me mtn is on strike I want to know how is that my problem coz I'm paying for something I don't have I who like to know if I can take further steps coz if I'm not going to pay the account I'm going to get lawyers letters but me not getting my stuff rite there's nothing I can do