Contract cancellation being made difficult

My MTN contract expired yesterday, i called the service center (135) to cancel however i received an auto response that the retention department does not work on weekends. Earlier in the month i calked to give an instruction to have my contract cancelled on the date of expiry however i was informed that i have to call on the day it expires rather. Today (11 October 2021), i called MTN retention department and after waiting on the call for a long period (30+ minutes) my call was not attended to.

What i find odd is that Mtn still opts in customers into contract renewals, is this lawful? Secondly Mtn does not communicate that the contract is ending but does try entice you to upgrade (which i will never do given the extremely poor service i received from MTN). Someone please advise there must be a law against this and possibly an action i can take against this entity.

Also when i call their general department the call gets answered immediately but as soon as i get transferred to retentions department noone answers the call.

Unlike my request to be refunded money that was incorrectly charged to my account that you never attended to upto date (ENQUIRY REFERENCE NUMBER *** - which possibly amounts to *****), Mtn please attend to my cancellation request.

I have also emailed your retention department (Enquiry Reference Number ***)