If you need to speak to a doctor on the telephone you can arrange for the GP to call you back the same day.
It is important that you give the receptionist a brief reason for your request, telling the receptionist the nature of your call, you are, however, under no obligation to give this information if you do not wish to, but it may assist the doctor in prioritizing your call.
No specific time can be given. If you are out when the GP telephones you or your phone is diverted to voice mail or a telephone answering service, they will make a note that they were unable to contact you and leave a message, if possible. They may or may not, depending on perceived urgency, attempt to contact you again later that day.
It is not usually possible, except in an emergency, to interrupt a GP during surgery hours.