The 33- year-old unnamed defendant said he couldn't cope when his girlfriend broke up their relationship in 2011.
"It was stupid," he told the court in Lyon on Thursday. "At the time my logic was that until she returns the money, she pays back for work I carried in our apartment or at least says thank you, I would not stop the calls."
For months calls kept coming, up to 100 a day, said Manuella Spee, the victim's lawyer.
"She tried to block her line but he phoned her parents instead and at her workplace," Spee said.
When the ex-girlfriend, a 32- year-old teacher, filed charges, "police noted over 100 incoming calls during the 90 minutes it took to file charges", said Spee.
When she finally said thank you during a meeting organised with the mediator, the harassment stopped.
The unemployed ex-boyfriend has not contacted her since.
The victim, who remains anonymous, "suffered a lot" said Spee, but since " has enjoyed a fantastic summer time, with no phone calls, and hopes it will last."