Customers could not call up on other networks and its own network in Punjab, Chandigarh and Panchkula in Haryana since early morning.
A senior BSNL official said there was a "technical snag" in the mobile exchange of the service provider in the city thereby disrupting services.
He claimed that engineers were in the process of restoring these.
Services to emergency numbers like 100, 101, 102 and 108 in the Punjab circle could not be restored as well.
