T-mobile is the only provider of 2G service that works with the GPRSbee modules that many people are using with the Mayfly, including about 40 stations managed by Stroud. T-Mobile plans to deactivate the network by the end of 2020, so anyone wishing to modernize their Mayfly’s cell technology will need to replace the GPRSbee with a 4G LTE board. We currently use the Digi Xbee LTE boards, which are available for purchase from a variety of online electronics distributors. There are no discounts for purchasing large quantities, so there’s no point in doing a group-buy. Since you paid for your stations and own your old 2G board, it’s up to you what you do with it. But we’ve had many of them fail after a few years of use, so they might be getting towards the end of the lifespan anyway, so I would be hesitant to pass used ones on to someone else.