No refunds - 1 month later

On the 9th of September, I claimed a refund of an airplane ticket, due to a system error. Mango said that they will refund me within 7 to 14 working days. I phoned again last week to follow up on the refund, whereby they rep**** that they have a backlog on payments and will pay me by last Friday. I phoned today to follow up again and they rep**** they have a backlog and will pay me by the end of the week!!! Surely, that is ridiculous! How can they say exactly the same in a 2 week period. They are lying. I asked to be put through to someone senior to assist me. I stayed on the line for 30 min! No one answered. Now I try and phone, but no one answers.