Products that don't work - will not give money back

I bought 3x Polaroid Kids GPS watches for Christmas, one worked it was for a chap in the office. I wrote to Homemark early Jan 2020, took a few emails before they answered me. I explained I had devastated kids with Christmas presents that don't work. I asked for money back. They fetch the 2x faulty watches, I asked for my money back. They give me 2 new units, they refuse to give me my money back. I've only asked for my money back now about 8 times. No customer service, products that don't work. Don't Buy Homemark