How do I return a product to Tom Tom and get the correct one sent out to me?

I ordered a TomTom watch cable. it is the wrong one for my sports watch. I tried to speak to someone on live chat 5 times during the working hours they state they are available and get the same response - no live agent is available. I found the telephone number for customer support. When I rang it they said they can't help me and I must go to live chat. I tried to cancel my order and get a refund and the site says I have no orders. Can anyone advise how I can sort out what should be a simple issue. I've never encountered such terrible customer service ever!