This is definitely something you'll wanna reach out to our Care team to get some assistance with this. Please reach out using the methods on our Contact Us page to get in touch with a representative.
Pre-paid plans are non refundable. tmo_mike_c had some good advice about talking to customer care to see if they will credit it for you but per the terms and service its not a guarantee. I'm not sure about the rest of what you said with the wearable but I would be happy to help further if you need more information.