Patients reported difficulties phoning Perth Royal Infirmary (PRI) on Monday.
NHS Tayside confirmed that telephone engineers had been at the hospital to try to rectify the situation, following a number of people contacting The Courier to complain they could not get through to certain departments.
A spokesman for NHS Tayside said: “There have been some problems with direct-dial phone numbers but people should be able to phone the main switchboard at the PRI.
“External calls should be OK. BT is looking into the problem.”
A patient, who wished to remain anonymous, said she had been telephoning PRI all morning and claimed she could not get an answer.
“If you phone a hospital department to, perhaps, try to cancel an appointment, you can’t get through to anyone,” she said.
“I phoned the main switchboard phone number but got a message saying the system was ‘out of order’.
“I phoned one number and it kept ringing but there was no answer. This was one of the hospital clinics but all I got was a message saying it was out of order.”
While the problem is investigated, NHS Tayside is asking patients to phone 01382 660111 and ask to be put through to PRI from there.