if you do a bit of searching, there is a thread on here that gives you a step by step instructions on how to get rid of that pop up. you have to go into your dialer and push *# and then some numbers and it will take you to the secret phone menu. i hated that pop up also but after i did that it has never popped up anymore.
here are the instructions
open the dialer and enter the following code:
*#6335623#
this will open "HiddenMenuWifiOffload" menu.
select "Disable WifiOffloading"
press OK
for the others they can be ignored or use an new keyboard.
NO ROOT REQUIRED FOR ABOVE TIP!!