Aircon re-gas

[SirHiss]

I have just been to a garage to get my aircon re-gassed. It ran cold just fine but I've had the car just over 2 years and I have no idea when it was last done so figured it was a good time to get it changed as I had just done full service.

I waited an hour and the tech comes up to me and says it was working before but now it's not. I give him a look of 'well what the fuck do you expect me to say'... He shrugs at me then goes back to my car and talks to another mechanic. He comes back and asks me if it's a single or dual system. Me knowing jack about air conditioning I said I didn't know. He explains that some large BMW's have dual aircon systems for the front and rear and the sticker in my engine bay had capacities for both and they assumed the larger one. So they filled my car with 900 (ml?) of refrigerant instead of 450. I was immediately concerned because that sounds like they doubled the pressure in my system. Couldn't that cause a leak?? While waiting I had a quick google and kept coming up with 450 as the aircon capacity and when I got home I checked the sticker in the engine bay and couldn't find any reference of 900. It only said 440 + 10 with some German written around it that I don't understand.

I was not charged for the procedure as he said he initially took 450 out and has put 450 back in. I asked if he meant new refrigerant and he said "some of it will be mixed with new, yeah". Isn't the whole point of an aircon re-gas to replace the old refrigerant with new? I didn't argue as he didn't charge me and I had to leave anyway as it had been an hour and a half at that point.

Was he a muppet? Is there likely any damage? Should I take it to a different place to have it done again?