bad service

In august 2013 I renewed both my phone contracts for 2 years and I was offered bis for 2 years at R14-99. On 31st December 2014 both my phones bis was cancelled. I call Vodacom call centre and they said that the problem will be sorted in 48 hours and they will have to listen to the phone call when I renewed my contract. when I spoke to the agent after a few days they said that the contract was for two years and the problem is sorted out. Every month end the cancel the bis for 1 phone only and I have to call and wait 48 working hours before my phone is sorted. I am frustrated with the bad service and when I try to find out why does this keep happening they can not answer me.