In accordance with the official PTCL website, the offer says, 

“Now all PTCL Broadband customers can obtain an EVO 3.1Mbps USB At No Cost by paying additional just Rs.500/month!”

There are 2 basic advantages of this offer;

One; you will get the EVO USB absolutely free

Two; an economical EVO package for just Rs. 500 a month.

For detailed information of this package, click