Miway Contract

I cancelled my contract with Miway on 8 May 2018 on their App. Meaning, the last date of my contract would be 25 May 2018. I then received an sms from them telling me that the retention department is going to give me a call. They tried to call me a week later(15 May), however I missed their call. I then received an sms on 21 May informing me that my account would be debited on the 25th. I do not understand why this is so as I have already cancelled my contract and obtained alternative insurance. After countless attempts of trying to contact Miway(who's retention department is supposedly ALWAYS busy), my contract still appears as active on their side.