More than 100 phone users were affected by damage to an underground cable in Weymouth.
BT engineers are working to repair the cable on Wyke
Road but it is unknown when the work will be complete.
Staff at Wyke Regis Health Centre are urging residents not to panic after continuing phone line problems.
Office manager Kim Carter said the Portland
Road surgery had been having connection trouble since Monday.
"We are concerned for our vulnerable patients who may need medical assistance.
"If anyone needs to contact us we are urging them to come into the surgery or ask someone to do so on their behalf.
"It this isn't possible then they can call NHS Direct on 0845 4647."
A spokesman for BT said: “Openreach would like to apologise to around 120 phone users affected by damage to an underground cable on the Wyke Road at the 'old bridge'.
“Engineers are doing all they can to repair the cable as quickly as possible but are not yet able to give a date when this work will be completed.”