[Q] Weirdest problem I've ever seen - Anyone can shed me a light? topic

Hi,

After learning so much on the forum, this is my first post.

I've never seen a problem like this and I did everything I could in order to solve it. I really ask for the help of forum members to shed a light...

PROBLEM:

When the internet is set on WCDMA/GSM or WCDMA only, it works for a little time (something between 10seconds to 5 minutes) and stops for a random time (something between 1 to 30 minutes).
If I make a call and it connects, during the duration of the call the HSPA works flawlessly (That is way too weird!)

FACTS:

1 - The internet works perfectly in the GSM only mode
2 - The place where I'm has a great reception for the HSPA (I have another phone to make sure of it)
3 - I did a complete factory reset and now I've KitKat 4.4 (installed through Odin) and the phone is rooted. The problem was there before all of that.
4 - As I said, during a call the connection works great without any problems at all.

Is there anything I can do? I complained to my service provider and they opened a file to send to the tech department.
My guesses are either there is something wrong with the SIM card or with my line. But I want to rule out any software or hardware issues...

Is there anyone that can help me?

Thanks