Still awaiting refund

I've had a bad experience with colour canvas which was sorted out with Groupon and they agreed to refund me. The refund was done in April. It is not reflecting in my account. I've been to the bank as requested by groupon only for the bank to tell me they need proof of refund. Groupon has sent me some sort of proof but the bank says that is not proof as it doesn't state any banking transaction and is purely internal records. Last week I went to the bank again and they said I need to speak to groupon as there has been no payment made. I've emailed groupon since and gotten no reply yet. I am tired of all the emails to you guys and the up and down running to the bank. It's time consuming and frustrating. I am a loyal groupon customer and expect good service. Please sort it out soon!!!!