Distorted Contractual Agreement.

I had a 24 month uChoose Flexi 55 Agreement with Vodacom. The contract started on the 1 April 2016 to 1 April 2018. I lost the phone 5 months ago. I asked Vodacom if the R 55.00 airtime could be loaded on one of my 4 other contracts that I have with them and they refused and said I should buy a new sim card of R 80-00 at their shop. The airtime started adding up on this account and when it was time to upgrade I cancelled this agreement. On the 1 March 2018 at 13:40 I cancelled with Palesa and informed her that they should recycle this specific number as I don’t want to receive airtime any longer when my contract end end of April 2018. She gave me reference number ********** 89. I called Vodacom in April again to confirm that I am not even on prepaid with this number and it is cancelled. When I received a statement form Vodacom on the 13 April 2018 I have a charge for this number that is called Subscription charges. I called Vodacom again and asked why I must pay this subscription as I have airtime credit that they won’t transfer; I am no longer using this phone and cancelled this agreement on time as per their contractual obligations. I spoke to Tsholofelo reference number 1- ********** ********** . He emailed a premature cancellation quotation to me with a return fax number ********** . I tried to fax the contents of this mail and their form to them but this line is busy all the time. I have another Agreement with them that I want to cancel in May as it will be 24 Months as well. Will I have this challenge to receive Subscription billing for a cancelled contract?