Bad service and false advertising

I place an order online for a item which showed they do have stock and also shows delivery 3 - 7 working days. I placed the order on the 26 November and made payment right away also made sure they did receive the proof of payment asap. I followed up the next day as I had a driver in the area to collect. Then was told it would be shipped the following tuesday. I followed up daily and nothing then I was told the shipment was delayed. I was promised numerous time that he will call me back but never did I get any feedback from the company. I also emailed daily without receiving any replies. Today when I called just after 9am I was told all orders was dispatch and he will call me back with a waybill nr which did not happen I the phoned back later to get the courier companies name as I will follow up myself and now they want to do a refund. this is ******** I should actually charge them interest on that amount