Our Staff Reporter KARACHI - Pakistan Telecommunication Company Limited is upgrading its telephone exchanges from Time Division Multiplexing (TDM) based technology to latest Next Generation Network (NGN) technology for providing better and improved services to its valued customers. PTCL inform its customers that it had started the migration series in Azizabad Exchange. The customers of Azizabad Exchange area are being notified that all those telephone numbers with the prefix series 3631-3637 will be migrated. There will be no change in the existing telephone numbers after the migration. There will be minor change of procedure for activation and de-activation of code barring service and other value-added services. PTCL regrets and apologizes for any inconvenience and discomfort caused to its customer during the migration. PTCL assures its customer to keep the outrage time as minimum as possible and to provide its customer with interrupted, smooth and levelled services. For any help or assistance customer can call PTCL help desk or call center agent round the clock on 1236. PTCL aims to provide its customer with good quality of service and anticipates the customer support during the migration process.