faulty blackberry units provided refuse to help

In March 2015 i upgraded to the BB 9720 and had the device for 2 months with endless issues, contacted the repairs dep which took them 4 weeks to collect then another 2 months to check whats the issue with the device, they never once got back to me with an update on the repair and i called in many times for an update with no info handed to me, eventually after 3 months after i called logged a complaint CS got back to me saying the software is faulty can they offer me a new phone BB Z3 this was only in October 2015 after i logged the fault in May 2015, we received the device end Oct and i have has non stop issues with the phone, it heats up when it charges, calls get lost, you cannot hear properly the call stalls, then 3 days ago the phone got so hot charging the screen cracked, i called in the booking and repairs to book the phone in, a lady by the name of Annalisa was to call me back for the IMEI no but still today no call, i don't want cellc to repair the phone anymore or offer me a new blackberry i want a new device or i will cancel my contract and sueue cellc for always giving us faulty phones and refuse to help us but bill us on time every month, i am a cellc client for 8 yrs