I experience the same problem. PTCL service is always patchy for me, recently it has been very poor. Opened a complaint for the same issue OP described. Their auto phone calls were driving everyone crazy so I just hit 1 for "problem fixed". The problem is never truly fixed until you disconnect PTCL.
It has been over 2 weeks at least with this latest problem and no end in sight. PTCL was offering a trial 4MB connection for the past 2 months - I guess they thought we would be so impressed by the blazing fast speeds we would stay at 4MB. Throughout the promotion, I never even touched 300KB/s on downloads, webpages loaded slowly and were often “broken”. Not only is PTCL incompetent, it is dishonest. They really take the P in PTCL seriously!