A telephone number was a number assigned to a telephone that was used to contact that phone.
In the United Kingdom, 999 was the telephone number to contact the police in an emergency, while 101 was the number used to contact local police. (TV: For Tonight We Might Die) 112 was the "European one". According to Clyde Langer, it was supposed to work even if everything else went down. (TV: The Empty Planet)
Liz Shaw's phone number was 01372 559 910. (HOMEVID: Unnatural Selection)
0207 946000 was the phone number for people to call if they had information regarding the whereabouts of Rose Tyler after her disappearance in March 2005. (TV: Aliens of London)
0207 946003 was the phone number of the company Rodrigo worked for as a tow-truck driver. (TV: The Parting of the Ways)
In 2006, after the Slitheen craft crashed into Big Ben, 08081 570980 was the freephone number used by the authorities in case anyone needed information about missing relatives. It was later open to any member of the public to report alien sightings. Jackie Tyler called it to report the Ninth Doctor, which set off a Code Nine alert in the British government. (TV: Aliens of London)
0301-566-9155-76544891 was the telephone number the presenter of Crime Crackers asked viewers to call if they had any information about the disappearances of children from Stratford in 2012. (WC: Tardisode 11)
The TARDIS telephone made use of the number 07700 900461 in 2008 and 2013. (TV: The Stolen Earth, The Day of the Doctor)
In 2016, Princes' Housing's phone number was 020 1108 70007. (TV: Nightvisiting)
95475949 was the TARDIS telephone number recorded in Clara Oswald's mobile phone under the entry "Doctor". Chandra Scindia used this number to contact the Twelfth Doctor in from 2315 Mumbai. (COMIC: The Swords of Kali)
+852 07700 900 781 was the telephone number used by Adam Lang to message Jake Willis to encourage Jake to find him in Hong Kong after he crashed down in the Soyuz spacecraft. (TV: Praxeus)