Cancellation is a war in MTNZA never attempt to take contract with them

Good day, I have returned all the router equipment in wonderpark store on 27 December, and the items were successfully handed over and accepted. Despite this, the service has not been cancelled to date. I have been sent back and forth multiple times without any resolution. When I attempt to cancel online, I am informed that the cancellation must be done in-store. However, when I visit the store, I am then told that the cancellation must be completed online. I was later advised that the cancellation would be processed online, which I followed up on, but there has still been no resolution now I’ve received a payment reminder, however the data allocation done for January I currently do not have the router with me, did not use it, kindly advise why payment is being requested for a service I’m unable to access, and whether this can be suspended or adjusted accordingly.