Mobilink 3G Throttling Speeds

I am using the Mobilink 3G connection and it has been around two months since I have used the connection, for the past couple of weeks I am getting some speed issues. Instead of getting around 7mbps speed I am getting between 1-2mbps speed.
I have not exceeded my data usage or been using the connection in another location.

Anyone else come across this kind of issue? What else may you suggest?

Yes I did call customer service, they told me to clear cookies from my browser, and I know they were just saying it as removing the cookies does not make a difference to the internet speed.