Handset submitted 3 times for repairs in 7 months

I submitted my Blackberry 9720 for repairs in Sept 2014 and in Jan and April 2015. The phone would switch off on its on and in the 1st two instances, only the battery was replaced. After the 2nd 'repair', the phone got worse and would power off more frequently. I also had to remove the sim card and put it back each time the phone swtiched off. In April, Vodacom said must I pay about R1'400 for them to fix the sim card reader!!!! I vehemently refused!!!!! In the meantime, I am paying for my contract by debit order, which includes a handset subsidy, and I had to borrow a handset each time the phone was at 'repairs', as it would take at least 3 weeks!!! So since April 2015, I have been paying for a DEAD handset. Had the phone not been switching off, I wouldnt have had to take out the sim card!!! I want to pay for a service that Vodacom should deliver!!