Testifying at Duffy's trial on Tuesday, Diane Scharf said the senator "already had a few phones through Senate communications."
"I just told him the truth that they would give me a phone, they would configure it, but they weren't going to pay the service charges," Scharf said.
"I think he said he would arrange for Gerry Donohue to reimburse me. Now, we did not want to circumvent Senate rules, we were just trying to serve the public."
The RCMP allege Duffy set up a $65,000 fund with Donohue to pay for expenses the Senate would not cover, such as makeup and personal training.
At the time, Scharf was replacing Duffy's executive assistant, Melanie Mercer, who was on maternity leave.
In her own testimony Tuesday, Mercer told court she was never asked to falsify claims that came across her desk.
Mercer, who worked in Duffy's office from his 2009 Senate appointment until the time of his suspension, described what she said was common practice in the office: having Duffy sign blank travel claims in order to facilitate paperwork.
"At the time, I thought it was very practical. I didn't think anything of it at the time."
"When you ended up doing the expense claims that way, it wasn't because you had any criminal or fraudulent intent?" asked Duffy's lawyer, Donald Bayne.
"No, I did not," Mercer replied.
Mercer testified she completed forms based on information provided by the senator and from information logged in his daily calendar.
Scharf told court she was run off her feet just to keep up with the fast pace of work in Duffy's office. Her work included handling different types of claims, including paperwork for travel, hospitality and living allowances.
"The phone would be ringing, emails coming in, mail would be delivered by the runner and he would send work in," Scharf said.
Scharf said the popular senator was in high demand.
"It was busy," Scharf said. "I did not take lunch breaks. I would eat at my desk because I had things that had to get done and because of who he was, people wanted to see him."
"I was going to ask you if this was a full-time position," said Crown attorney Jason Neubauer.
"And then some," Scharf replied.
Scharf also told court she received emails from Duffy at the wee hours of the morning.
"He works 24/7. He would send me emails on Saturdays and Sunday," Scharf said. "He didn't call to chit-chat, it was always work."
Duffy has pleaded not guilty to 31 charges of fraud, bribery and breach of trust.