Incorrect Billing Date

I am starting to be irritated by miway. They keep debiting my account on the wrong day. I have been complaining since October 2015. And each consultant promised to get it sorted out. The worst part, was when they debited my account in January, whereas in December they debited it twice for both December and January, of which I was okay with it, but to debit me again in January??? On the wrong date???... This caused a huge inconvenience in my budget for that month. And today I log onto my cellphone banking to discover that, again they attempted to debit my account. Now they smsed me saying they didn't get the premium and I won't enjoy my cover... We agreed that they should debit my account on the end of each month because that is when I get paid. Will this ever stop?. I am officially fed up.