Firmware upgrade for MC5725?

I have a Sierra Wireless 3G modem (Verizon) with a firmware version of P2006004 that I am trying to keep in service as long as possible. Verizon has made some changes around here and now I am getting repeating cppm: busy errors with 1 minute suspended connection and then a short connected time I was hopeful that a firmware upgrade might make this old modem more compatible with the Verizon network. Is there such a thing? Where could I find it? Any help is much appreciated?

Better to contact your distributor…