alloy wheel nuts

[steve1968]

just been to have new front tyres fitted at the same place i had the last (used) ones fitted , 6 months ago, and they have broken 8 of the nuts trying to get them off, they put them on , there is still part of each nut still on so the wheels still won't come off.
the car is an 88 ,911 is this a common problem or bad workmanship on there behalf?
the lad who did the original job left last week, luckily for him.
any ideas how to get the last bit of nut off without damagind my wheels .