You can scrap the receivers and shred the cards. If they still work, I would try to find a buyer first. A 3100 is still a valuable receiver to many people and some may prefer a 4100 to newer models. Just be aware that scrapping the receivers will leave them on your account indefinitely, even if you call Bell and try to remove them from your account. Technically, the cards belong to Bell but I've yet to hear of them wanting them back, except for upgrade purposes.