The girl was shocked after a detective from the Metropolitan Police asked her to contact him as part of a homicide investigation.
Her father, Paul Louden, from Baberton, was furious when he phoned the officer to find the number was linked to the murder of a Mexican transgender prostitute.
Mr Louden had bought the brand new iPhone from a Vodafone shop, but said he had to prove it was being used by his daughter and that he had only received the number in June.
Vanessa Santillan was found strangled and battered to death in a flat in London on March 28. The 33-year-old had migrated to London from Mexico in January and is believed to have been working as an escort.
Joaquin Gomez Hernandez, 23, was charged with her murder and is waiting to stand trial.
But Mr Louden, who owns a garage in Longstone, said the incident had left his daughter “in bits”.
He said: “We bought the phone for my daughter as her friend had emigrated to Australia. It was primarily for them to Facetime each other.
“The only other people who had the number were family. Then she got a message from a police officer who said he was with the homicide department in the Met. She understood what it meant and was in tears.”
Mr Louden said the police told him the number was linked to Ms Santillan’s old phone and had been disconnected during their inquiry.
But officers monitoring the account became aware when the number was reactivated.
A spokeswoman for Vodafone UK apologised for the upset caused, but said the call from the police was “entirely beyond” their control.
She said: “We were very sorry to hear that Mr Louden’s daughter was upset by the call but this was entirely beyond our control, and we have no record of the police contacting us about the number in line with usual process.
“The number was first connected on our network by a previous customer on August 18, 2014 and was disconnected on November 7, 2014.
“Six months after disconnection, fully in line with our processes which aim to comply with Ofcom’s request for us to be ‘economical’ with the issuing of phone numbers, the number was re-allocated to Mr Louden.
“To be clear, there was no activity on this number between November 2014 and May 2015 when it was issued to Mr Louden. As far as we are aware, the police have still not been in touch with us.
“We agreed to take the handset back and cancel Mr Louden’s agreement.
“We also offered a goodwill gesture of £25. Mr Louden has refused this offer.”
The Met declined to comment.