Taking Money without being signed up with Rain

I initially got a 4G package from Rain. Unfortunately the network wasn't strong enough for me to use as I am working from home. I've cancelled the package within the first week and received back my full refund as promised on their website.

The problem is, at the end of March, an amount still went off my bank account for Rain. I've phoned them 3 times last week. The first person told me someone will get back to me within 24 hours. 6 days and 3 calls later, no one has yet come back to me.

I have no idea why they debited my account. Why was my money taken if I wasn't signed up with Rain anymore.