Vodacocom bad service with cancellation request

Cancellation of two numbers on a contract of 7 lines that have expired .On the 1st March i called vodacom cancellations as there were two numbers expiring .They informed me they would cancell the 2 contracts and convert the accounts to prepaid .I recently received my bill and the 2 contracts are still active and been charged for for April .Poor show that i should pay for their mistakes and i have requested a refund ,but no one responds to my requests .The next step would be to contact Icasa i suppose .