Apple Watch SE2 Compatibility Hassle and Vodafone Customer Service Fiasco

I recently purchased an Apple Watch SE2 from a Vodafone store. Upon trying to pair the watch with my iPhone 7 at home, I was disheartened to discover that they were incompatible. I immediately contacted the store, but they refused to accept a return, citing that the box had been opened. A week before the 14-day window expired, I made another call to the store, hoping for a solution. Shockingly, the store representative insulted my consumer rights and rudely hung up on me. In desperation, I reached out to Vodafone directly. They assured me that my refund rights were intact and that I could return the watch within the 14-day period. They initiated an investigation, but it's been over a week, and there's been no progress. Now, my return window has closed, and I'm stuck with a non-functional watch. To make matters worse, the store hasn't provided me with an invoice, preventing me from seeking help from BTK or Consumer Rights. I implore Vodafone to finally resolve this issue.