BAD COMPANY Till slip advertising

We agreed to do a till slip marketing campaign with a company called Till slip Advertising. We paid the Deposit in August 2019. We were told it will take approximately 1 month before all goes live. In september when we called Grant we were told that there was a delay and they will have it done the next month, and so it carried on till Jan 2020. We were then assured by Dave that we would be refunded, We have been following up, but now our calls do not get answered any more. We still have not received our refund.