Been waiting for more than three months !!!

I ordered and paid for an Garmin product on 2014/11/10. Delivery should have taken at the longest 4 weeks. Months after delivery should have taken place I still have not received anything. I tried contacting the seller various times as they claim on there website they will respond in 24 hours, this is also not true as they do not reply. They have supp**** an tracking number on a previous occasion and told me to go to the post office. There tracking number is untraceable and the post office do not know anything about the number as well.