PTCL-DSL package

In September 2009, I got DSL connection on my landline No 36315169 under student package with one month free offer. On expiry of free offer time-limit bill received according to student package but from the very next month, DSL charged at normal rate without any intimation to me.
I approached all the concerned authorities of the PTCL through personal visits and provided copy of university ID card, emails, letters, but of no avail. Now I approached the PTA through email but still no corrective measure in my DSL charges. I request all the concerned authorities through your esteemed paper to look into my complaint and the DSL charges be revised according to student package or to disconnect DSL immediately with adjustment of all excess amount.