I was also facing the same issues back in 2012. Lodge several complains but in vain. Then eventually I got an email address of their head office and escalated the issue and then it was fixed.
The issue is contention ratio in your area. Means the number of users are high in your are but the bandwidth provided by Ptcl is not sufficient for your area due to which all users in your area face speed issues during peak hours I.e. 6 PM to 2 am. So they just need to increase the bandwidth of your area from back end and hence the issue will be resolved.
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