why is GPS location service charging me data cost while i am still on wifi connection?

[Parth Patadiya]

I am currently using Xperia M.
Unexpectedly my phone was bootlooped and i had to flash device using flash tool by androxyde and downloaded official firmware from sony pc companion and made firmware in flashtool and flashed my phone.
But now when i switch gps on while using data pack from my network provider it doesn't charge me and when i use gps with wifi it says session cost *** so n so .I mean for what is this costing me.