How to Cancel M+ Membership Payments
If you pay by WorldPay you will get a payment confirmation each month that also gives you the cancellation link. Look on the last email as you will need what's called the Worldpay FuturePay Number. Much the same with PayPal.
Worldpay Page for Shopper Help FuturePay Account (Recurring M+ payments)
Then click on link "How do I cancel my agreement and stop recurring payments being debited?" - NOTE: You will need your WORLDPAY username and password. If you lost it there is a password reminder function on the WorldPay website. (Click on link marked: I've forgotten my username and/or password.)
Log in to WorldPay HERE
PayPal Cancellation Page All explained simply on the PayPal website
If you need step by step help this webpage gives really clear instructions of how to cancel.