"The victim considered the text messaging normal at first," Judge Cameron said.
Munro asked the victim how old she was. She told him she would be 15 soon.
Munro then sent a message asking her out again, to which she replied, "I don't know you."
He asked other questions, including what colour her bra was, whether she would go to his house and watch movies, and whether she would have sex with him. He also asked for nude photos.
Munro offered to top up her cellphone "numerous times", and sent her a message saying he would pay her $100 if she would have sex with him. Judge Cameron said the victim considered the message "rude" and "inappropriate" and stopped replying to his messages.
Munro then started calling the victim, and again asked her to have sex with him, to which the victim replied "No, I'm not a prostitute."
She told him if he didn't go away, she would call the police.
Police investigated Munro in March, 2014, and he was arrested on May 23 that year.
On June 4, he sent a letter to the court, addressed to the judge, written on New Zealand Police letterhead.
It said police wished to withdraw the charge against Munro.
On June 13, Munro sent three texts to a caregiver, pretending to be a member of the police, Judge Cameron said.
The text messages were designed to make it look like another person had committed the original offence.
Munro also contacted the manager at 2degrees and asked him to lie to police about him buying a sim card.
He sent police an email, pretending to be the manager, trying to make police believe another person had bought the sim card.
Munro has previous convictions from 2011 to 2015, including five convictions for dishonesty-related offending.
"The defendant clearly has a propensity to deceive others when it suits him, or attempt to deceive them," Judge Cameron said.
"This defendant, without interventional programmes, poses a significant risk to the public and, in particular, young girls.
"Indeed, by his inappropriate social behaviour, puts himself at risk of harm from others concerned about that behaviour," he said.
Judge Cameron said Munro suffered from "limited intellectual functioning".
Crown prosecutor Lance Rowe told the court he would have sought a "harsher" sentence against Munro, had it not been for his intellectual issues.
A pre-sentence report assessed Munro as being at moderate risk of reoffending.
Judge Cameron sentenced him to six months of community detention with a 7pm to 7am curfew, and 18 months of intensive supervision.