How do I cancel insurance payments

What is the process for cancelling the insurance for a broken, lost or stolen phone. I have five phones on my account and originally purchased insurance for each one when it was brand new. Now I'm paying almost $50 a month, $600 a year, to insure three year old phones worth less than $50 as trade-ins. Bottomline is we've never had an actual problem with any of the phones so we're just wasting $600 a year. How do I stop these insurance payments as soon as possible? Thanks in advance. michaelpaul50