Defence lawyer Shaun Russell asked for a discharge without conviction for Banks, saying the consequences of a conviction would be out of all proportion to the offending.
Mr Russell said Naked Bus provided its drivers with a company cellphone and would text updates to the drivers if they needed to make specific changes to pick-ups or drop offs.
He said the drivers were to check before leaving, but quite often messages came in while they were on the road and the drivers checked them while driving.
"He accepts he was using the work phone but he never texts on them," Mr Russell said.
A conviction would prevent Banks from continuing his career as a professional driver, which he had been doing for more than 40 years, Mr Russell said.
A disqualification would also affect his ability to retain his licence to carry passengers. Banks had no previous convictions.
But Judge Simon Maude said the summary of facts, to which Banks pleaded guilty, made it clear that he was using a cellphone while driving and this was supported by the photograph taken by the passenger.
Judge Maude said the matter was too serious to discharge Banks without conviction.
"The use of a cellphone while driving is rightly regarded by the public as a serious risk. The seriousness, in my view, heightened when the driver is in charge of a large vehicle and, significantly, is a professional driver for members of the public," the judge said.
"It's aggravated by the use of two cellphones over a relatively prolonged period. It was a conscious act. It was wilful and careless and exposed members of the public to risk."
Judge Maude said a disqualification was necessary so that when he reapplied for his P licence the authorities could evaluate whether he was a fit and proper person to drive a vehicle with members of the public in it.
He sentenced Banks to a $100 fine and disqualified him from holding or obtaining any driving licences for six weeks.
