friends with non-smart phones cannot see my SMS but they can see MMS

[volcalisa]

I've had a Samsung Galaxy S3 for 2 months. Ever since new, everytime I text to someone with a non-smart phone, all they get is a blank message window, or the first letter of each word. However, if I insert a photo and the text goes as a MMS, then the person can read the text and see the photo. if i type more than 160 characters and the text transfers as a MMS automatically, the non-smart phone still does not show the text (the words). I've dealt with the issue by inserting photos in all my texts, but I'm hoping there's a way around this. TMobile is my carrier and their customer support has been 0 help. thanks.