Error msg when using unlocked V195s (TMobile) with ATT.

[Drifter447]

I have been informed that by deleting the app "My Faves" the problem would be resolved. Unfortunately it did not happen.
The phone works fine with the ATT Sim Card, as long as you do not turn it off.  When you turn it back on, after 10 or 20 seconds, it receives the following  text message:
"453 Error Invalid Number. Please re-send using a valid 10 digit mobile number or valid short code. (then it shows a long line of numbers, about 40 digits). The message ends with the sender's number: "From +1121611611".
I used P2KtoolsVs to access the phone's files. I wonder how could I get that problem solved.
Any help from you guys would be greatly appreciated.

[Drifter447]

I am happy to say that I, finally, solved this problem once for all.
Apparently, everything related to T-Mobile had to be eradicated from the phone. So I decided to re-flash it with a generic firmware pack. Since I could not find the firmware (R3443H1) for the V195s, I used the R3517 for the V197. Using the P2KtoolsVs, it was quite easy, and now the phone works perfect with the ATT sim card (no T-Mobile icons, no "My Faves", no error messages...).  I haven't checked "Internet Access" yet, but I think I will never need that, with this phone, anyways.
If any one ever faces this problem, I will be glad to help, with more details.