Does not want to refund or honor double money back guarantee

I ordered one there products: Fixed wireless LTE-A. The product gave a ********** experience. I submit a return within 7 days of the router's delivery. This was on the 3 October 2017. They collected the router and SIM card the next day.

I have phoned multiple times and sent several emails. They promise to refund but never do. If I do not get a resolution from this complaint, this I will go to the ombudsman.