Android Help - Unknow misscalls and incoming

Hi i am having a problem
it occurs when i get a misscall or incoming call from an unknown number
...basically as soon as i hang up or go to view my call log on my android after a few seconds the "unknown" straight away renames it self as someone from my contact list eg "loo" and wen i click to view it gives all the information it will give as if it is as unknown number.

My problem is that when i look at my call log my misscalls are from "loo" and it does not say unknown so can anyone tell me how i can change these setting.. i mean all the info it gives is correct but i just dont want it to show my contacts name.

btw i have a t mobile pulse mini

please help and thank you