GPD Promotions Systems In review: I returned the vacuum cleaner, but I didn't get the refund

I have bought the vacuum cleaner from GPD Promotions Systems Inc. The sales person came to my house and offered this vacuum cleaner. But after some time I decided to return it and filled the cancellation form. I have received the confirmation that someone would come and pick the vacuum cleaner. The person took it away 4 weeks ago and I continued to wait for the refund. I still didn’t get it. I am worried about it.