Try calling 111 if you need assistance but it's not an emergency. The operative will ask you questions about your condition and suggest the most appropriate action to take.
Calling 111 may result in the operative advising you to call your GP. Do this as soon as you are advised to or if you have a condition that you feel requires an appointment.
You should only call 999 for an ambulance in a medical emergency where it is obvious that you or another person has a serious life-threatening illness or injury.