I have 2 Nokia Lumia 521 for tmobile that I switched to straight talk 3 months back and still can not receive or send MMS messages. It is very frustrating as when I called Straight talk they told me no guarantee on service was made and told me to have a nice day. I have tried unsuccessfully for the last few months to fix it myself by researching the internet but I am having no luck and am very frustrated. I have tried every setting possible but can not get it to work. Any help would be greatly appreciated!