I have had endless problems - they just don't seem to listen to requests very well and some of them have a real attitude on the 'phone.
I have called at least twice to change credit card details and left messages - no-one has called me back. Called again just now and got stroppy bint as dared to mention my phone calls hadn't been returned - no hint of an apology.
Have asked for three or four other things in the past and they haven't bothered to come back to me.
they don't treat their sitters very well though. I had to cancel 3 babysits over the course of about 2 years.
I used to be a sitter for them but cancelled once due to me being sick (didn't want to pass on a sick bug!), once due to my FIL being taken into hospital due to cancer and my DH wanted to be with his dad and a third time when my daughter had emergency surgery aged 4.
They told me they didn't need unrealiable sitters that weren't commited!
I earn a lot more than minimum wage outside of working for sitters (which is about all you earn with them) and would never register with them again.