Poor fitness device support

Was very excited when I was informed I qualify for a fitness device offer through my vitality rewards. I selected a device through the vitality prompts and was then contacted by Tel"JOY" to sign a contract for my device which would be linked to my rewards. The watch has been a problem from month 1. I received no technical support from your or teljoy so reached out to Garmin. They several times assisted me in resetting and repairing it to try get it to function. This was already a frustration. My arm then become sore and itchy and upon removing the watch to charge it found burn wounds on my wrist where the face of the watch rests! I again called Garmin and they advised me that they unit is probably faulty. I logged this with Teljoy. Whilst prompt in their response, they offered no assistance or resolution, 2 weeks later and this is still unresolved. After threatening to cancel my contract they have now agreed to investigate although cannot seem to get their internal communication right to do so. And as you guessed, Vitality is of NO support. I cannot track my exercise goals with a device that burns my arms, which means I have to pay for a faulty device. discovery will not budge on this as it is not an apple device so they do not acknowledge a financial liability linked to the goals. And empty promises to follow up or get back to me from your call centre. I have requested to cancel my contract teljoy. Will most likely also cancel my vitality as there is no point having this if I don't have a device that can track fitness and I will certainly not be getting one through discovery or vitality!