No response from MTN insurance

I issued a claim 26 November 2015 against MTN Equipment insurance for my son's phone that would not start with the reference number\((***0) . After many issues of no communication and no loan phone as promised in the contract , I received the phone on the 5th February. Now it gives me exactly the same problem as before, only a month and half after repairs. I sent a mail and usually receive an automated response, but this time I received no acknowledgement of receipt. Surely there must be a guarantee on the workmanship of repaired products before I have to pay the next payment which is double the amount of the first time? And once again there is no response to communication to MTN."