Vile Thomas Adams, 29, was arrested in June last year after police found the teenager in his bedroom after she had been reported missing just hours before but he continued to contact her from his cell.
Bradford Crown Court heard police were made aware in October 2019 that Adams was still calling his victim from prison after her father seized her mobile phone.
Telephone evidence showed in just over six months while being detained, Adams had made 3,506 calls to the girl and they had exchanged 12,975 texts between them.
When prison staff searched Adams’ cell in February they found a phone charger, photos of the girl, and a phone book with her contact numbers in it.
A segregation cell he had been placed in was also searched which led to the discovery of a smashed up mini mobile phone which had been hidden within the pipework of the cell.
Adams had provided prison staff with a false name for the teenager when her number was listed an approved contact, the court heard.
Adams from Bradford, West Yorkshire, pleaded guilty to charges of engaging in sexual activity, inciting a child to engage in sexual activity and engaging in sexual communication with the teenager.
On Wednesday he was sentenced to eight years in prison, a five-year extended licence and will be a registered sex offender for life.