not all cell phone have a modem,and you cannot send at command if modem don't exist,my lg phone,don't have a modem. it's not me have request help!!!,so respond to the poster,not me!!!
so,if good idea to test with dongle before try with bluetooth module,i've tried many phone to do my project(without gsm module). cheap phone don't have a built in modem,or not client enabled by the provider(and firmware),i know,i've tested and talked to the provider,virgin mobile dont allow to use modem
but now i use telit gm 862 module with sim card and no contract,only sms plan with Rogers.
my project is in use at the waterplant in my town