Wateen Wimax.....eating Mega bytes

I just got a wateen as a gift from my friend in wateen. No doubt good service. but one thing that is noticable, bytes consumed too fast. Means as soon as the connection is established, it starts data flow in Mbs. Altough i havent browsed any heavy sites like youtube or any other such streaming site. but data keep flowing on higher rate. i closed internet explorer but it was flowing and flowing. I was concerned because it has limit of 5GB of data flow, which i was thinking, is enough but it wasnt. i have used almost 30% date flow in just 3 days. and from last 2 hours, i was just chating to a single person on msn and it took 50MB for this. just chat and this site. which is opened once and still i m writing into it. I installed a firewall to control the programs that are trying to automatically update but all in vain. I dont know whats the reason but i thnk it might be some trick to finish my data flow limit :). If some one from you know any thing about this do tell me. i will appreciate that.