A friend of mine complained to me about mtn deducting a sum of #50 weekly from his mtn line. I recalled having the same issue, and i can attest to the fact that it is really annoying and fustrating, especially when you just recharged and wants to make a long call. First, i placed a call to their customers care and after the long wait and prohaha, i was able to stop the service.
So to all my friends who don't like calling their customer care for one reason or the other, you can simply follow these procedures/steps to opt of the mtnplay service.
Firstly, insert the sim card in an internet enabled device or a modem while making sure their is a sufficient amount of mb in the sim card. With that in place, visit wap.mtnonlineplay.com and click on Mtnplay and you will see something like this
Then click on the 'My subscriptions' to see the services you are currently subscribed to and you would be shown the service(s) you are subscribed to, click the ones you want to opt out of and you will see the 'unsubscribe' option and the rest is history.
Source:http://techstine..com/2015/05/how-to-stop-mtnplay-from-deducting-your.html