Changed numbers and old number coming up when I text people on ATT network.

I had a sprint number, ending in 5571.  When me and my fiance switched to ATT, I could not transfer my number over yet, so I got a new number, ending in 0671 with my iphone. I had this number for a week before I was able to port in 5571 into the iphone.

When I text my father with the new 5571 number, it still came up as 0671 on his phone (he never even had that number stored as a contact for me).   Same thing with my mom, same thing with my fiance.  They all have iphones, all on ATT, and I had texted all of them previously when the iphone was still tied to 0671.

So I text a friends wife, someone who I had never text before in my life.  She does not have a iphone and is NOT on ATT.  When I text her, it came up as 5571 which was correct.

I then text my fiances freind who IS on ATT, and DOES have an iphone, and whom I have NEVER texted before and it came up incorrect as 0671.

So now I have narrowed it down to its either only happening on the ATT service, only on iphones, or a combo of only on iphones on the ATT network.   Does anyone have any suggestions?   

And also, if the number comes up as the incorrect 0671 and they reply to that text, i still recieve it.   AND, get this, if i CALL them, it will come up correctly as 5571.

Heres my tests so far.

ATT sevice, iphone, texted before from 0671 =  comes up 0671

ATT service, iphone, never texted before from 0671 = comes up as 0671

Other service, no iphone, never texted before from 0671 = comes up 5571 (correct)

ATT service, no iphone, never texted before = have not done yet

Other service, iphone, never texted before = 0671