Shocking Service level.

My vodacom contract expired January 2017, i followed the correct processes in which i supp**** a a cancellation letter one month prior to the contract expiring, which i receive a reference number, long story short is that more than a year later i receive a statement saying i owe vodacom money, and after numerous attempts to cancel the contract nothing has been done, the has effected my credit score badly due to vodacom's inability to follow a simple request, each time i call or mail to try and rectify the situation i either have no response or im directly to every department who is unable to assist me, shocking service!!!