Digimon World DS

I'm trying to Digivolve my DemiDevimon into Devimon without cheating for Scan Data on Devimon. Does anyone know how to DECREASE A Digimon's friendship with you? I need DemiDevimon's friendship to be below 20% before I can digivolve and it's currently above 20%

From googling:Decreasing Friendship
You can decrease a digimon's friendship in the following way:- Don't talk/train Digimon in farms.
- Not enough Digifood when Farm report is announced.
- Digimon's HP is reduced to 0 during battles.From neoseeker