[friguy3]

you cant use MMS without that line so put it in. go to the folder where it should be and click +add value+, then type in X-VzW-MDN exactly like that (keep it on string), then click ok and put in your 10digit phone number...click ok to get out and try it then.

and yes...hard resetting will erase everything you have done and put you back at the begining.