BAD SERVICE AND REPAIR JOB

I am a client with vodacom. In June 2017 I took out a new contract and got the iPhone 7+ after waiting two weeks due to NO STOCK AVAILABLE. Three weeks ago I took the iPhone in for repair as the wifi and camera did not work properly. Yesterday I received a "new" iPhone 7+ as the original one was repaired but it did not pass the quality check. When I switched on the "new" iPhone 7+ it had more problems than my original iPhone, problems with the new one includes, home button faulty, wifi not working, can't make calls and when going into settings the phone just freeze. This phone was immediately handed back to vodacom as the salesman indicated there is a fault with the phone. Now this "new" phone is sent back to the advanced repair center for an assessment, where as the repair center in Durban has confirmed that the phone is faulty and they will request for a new , new one to be issued as at this moment they still waiting on the assessment report. So how can a phone skip 3 quality checks and be handed to the customer and it becoming the customers problem and being without a phone for more than 3 weeks and counting as the client is waiting on the reports. Needless to say, I want to cancel my contract as I am very unhappy with service delivery, but with clauses in place I cannot cancel my contract.