The outage to fixed lines started at 08:42 due to an electrical fault at Sure’s central exchange in town which affected copper fixed line services.
Anyone still on the copper network in those areas were affected, including hundreds of businesses and key public services.
Emergency lifeline buttons, a form of personal medical altering equipment, were reportedly not working either as they were routed through the same exchange.
The telco has said sorry for the outage, which lasted nearly three and a quarter hours for some.
“Engineers were deployed immediately and by 12:15 all services were restored. We apologise for the inconvenience to anyone affected by this outage,” Tracy Kirby, Head of Customer Services, said.
“Mobile, broadband and fibre landline services were all working as normal throughout this time.”
Bailiwick Law Enforcement had encouraged those impacted to make emergency calls on mobiles during the outage, while businesses who went without telephone urged contact to be made via email or on social media.
“As a precaution, if you know a vulnerable person who may have been impacted, and does not have a mobile, we suggest checking in on them,” Ms Kirby added.
Anyone still experiencing issues is encouraged to contact Sure.