My installments are debited double

On the 13th of December Lewis debited double amount of my instalment. On the 16th, I went to the store and explained what happened, they asked me to bring my bank statement and ID copy, I did and never heard anything from them, they didn't even refund my money. On the 6th of January I called following up on the refund, the lady told me I will not be able to get my refund because my account is in arrears. Okay fine I left it at that. Now on the 25th of January they debited double again, I went to the store again to enquire, they asked for my bank statement and ID copy, I gave them and still I haven't heard a word from them. Been trying to call them but they tell me they busy, they will call me back and they never do. I don't know what to do now.....