Bad service

I registered my sister's baby showe yesterday but I unconsciously put her ****en name and not her married name. I went back to Baby City for them to amend the name but I was told the can't do it because it was already in the system. This for me just seems that the branch manager and the lady at the till where just being lazy. I made same mistake with Woolworths and I was able to change the name without any hussles! I urgently need to change the names as I need to send the invites tomorrow. The registry number is R/09/2015/105