Poor service when contracts ending

I currently have a LTE Business Data with Vodacom which was a 36 months contract. I made payments on time for 36 months. The full term of the contract has passed, now when I want to end the contract l got informed that I need to send an email to cancel, I don't understand why because the contract was for 36 months. I sent the email on the 14 December and have since not had a response for over 10 days and when I call customer care to query why I did not get a response I am being told that no one has attended to the case as yet. I am so frustrated when it was time to sign up to the contract the service was efficient now that I am leaving Vodacom I must send emails to cancel and they not attended to those emails and basically forcing me to stay with them.