Nokia 6620

when people call me on my 6620 it shows two of the same caller id. it has the white bubble type with an overlay of a rectangled caller id box with the same number over it. the overlayed one disappears after a little bit but when my friend had the same , literal, phone and it didnt do it for her. it is an unlocked att 6620, and i am using t-mob service on it firmware 2.14.1

any insight would be appreciated