AT&T iPhone 4S data connection problem

Hi guys.

So I have the AT&T iPhone 4S 16GB, and I am a unlimited data plan carrier.
I enjoyed my device until end of January where my data connections have been really slow.

Its not always. This is the problem.
It gets slow for a while, literally giving me no access to internet, map, and even using the speedtest app.

But then it gets all better again. Starts off around 92ping, 0.35 mbps down, 0.21 mbps up.
Then it gets better a bit and goes up to 1.2 mbps.
When its acting good, it becomes near to 4 mbps.
As you can see, its definitely a problem.
Yes, I do have all bars on what they like to call the "4G".
And yes, its not the location.

My friend's iPhone acts fine and I tested in many civilized places like SFO Airport, LA, etc.

Im starting to think that this might be because I am the old unlimited data carrier.
I do use a lot of internet since I render Maps, open safari's, update apps, etc.

Do you guys think this is the problem?
Or can this be the iPhone's problem? i.e. antenna failure, case fault, ....

Thanks in advance.

 

My friends iPhone and my fathers iPhone (both AT&T) were fine tested at the same location and time.

However, Im the only unlimited data plan carrier so I thought they sowed my internet down.

 

Tried that 3 times yet I still get the same results...