Mtn
Paying for a phone, but i dont use it

I took a contract phone with MTn since January this year n their phone was giving me problems since day one, till i took it back n they gave me a brand new phone same model blackberry 9360.and the same phone they gave me was also not working properly i took it back again but it was never fixed from march until today. my imei;; 351602059031045 I'm now complaining to hello peter as my last option, please help