SALAM EXPERTS.

I Have a problem . i am using ptcl dsl broad band .with LAN SETTINGs.
i want to now change it into wifi ..if i order this to ptcl they charge 100 rs extra permonth. but i heard that if wifi modem is attached to even lan dsl connection wifi can be run.
i have a wifi modem of "HUAWEI TECHNOLOGIES MODEL NO. Echo life HG520C "

Can any one help me that how can i use this wifi modem to my ptcl connection.?