refrigerant

so i'm living in Eastwood Le Grand 2 and my unit is a loft type. I recently bought a new air conditioner, but on the day of installation, the technician discovered that my old AC uses a different refrigerant from the new one. since the existing copper pipes are concealed and would need to be reused, they said the pipes must first be thoroughly cleaned to avoid contamination.

the issue is that the piping runs from the loft area all the way to the balcony, making the job more complicated. Because of this, the technician decided not to proceed with the installation.

now I'm not sure what to do. Should I look for another authorized installer from the same brand, or should I ask the building administration for assistance since the pipes are concealed and they may have records of the unit's piping layout? I'm worried about potential issues that could arise during the cleaning process, but I also need the installation to be done by an authorized technician to keep my warranty valid.

honestly, this whole situation has been really stressful, and I don't know what the best next step is.