A GRAFTON inmate will serve no extra time in jail for being found in possession of a mobile phone while in custody - an offence which seems to be plaguing the local correctional centre.

Appearing via audio-visual link, Brandon Lavis pleaded guilty in Grafton Local Court to two drug offences dating back to March 23, and one count of possession of a phone while in custody.

The drug matters, deemed by Magistrate Jeff Linden to be the least serious offences, related to a search warrant on a South Grafton home in which two plastic bags were found with cocaine and methamphetamine in them.

Lavis, who was in the house at the time, admitted they belonged to him.

He also admitted guilt in relation to the mobile phone, which was found by corrective service officers while he was serving time in Grafton Correctional Centre for drug supply.

A mobile phone charger, secreted under the bedding of a mattress in a cell, was discovered during a cell search on June 17.

The next day a search of another cell revealed a Telstra touch-screen phone hidden in a sock, behind a toilet sewerage pipe. An active SIM card, found hidden under lolly wrappers in an exercise yard that afternoon, contained the home and mobile numbers of Lavis's girlfriend.

In court, the police prosecutor argued the offence warranted an extension of time served , saying Lavis "shouldn't just get a free kick out of having a mobile phone in jail".

He noted the offence went to the heart of the security of the corrective system.

Magistrate Linden, however, spoke to the fact Lavis had used the phone to contact his girlfriend, saying that while he could not condone the inmate's actions, he could understand them.

Lavis was convicted and sentenced to 15 days for the offences, to be carried out within his current term of imprisonment, meaning he will serve no further time. He will be eligible for release on October 27.

It is the third time a Grafton inmate has been sentenced this year over the possession of a mobile phone.

On August 21, Grafton inmate Neville McGrady successfully appealed the severity of a sentence of 12 months for mobile phone possession in district court.

The active phone was found during a search of his Grafton cell block, on April 8, and on appeal his sentence was reduced to 11 months and eight days, backdated to April 10.

Disgraced Olympic kayaking silver medallist Nathan Baggaley also had a month added to his sentence in June after a mobile phone, hidden in a hollowed-out loaf of bread, was found in his possession while he was serving time in Grafton jail.

A Corrective Services NSW spokeswoman admitted mobile phones posed a significant challenge to correctional officers across the globe.

"Prisoners will go to extraordinary lengths to introduce contraband and inmates most likely introduce miniature phones through internal secretion methods... and CSNSW staff cannot undertake internal searches," she said.

"Corrective Services NSW is focussed on detecting and intercepting all contraband in NSW prisons and takes a zero tolerance approach," she said.

She said searches for illegal and banned items were conducted daily on prisoners, visitors, cells and all common areas.

Anyone caught bringing contraband into prisons face penalties of up to two years' imprisonment, or ban on visits of up to two years.