Hi Mammamu,
I think that Oh Knickers advice is probably the best way to approach the situation.
Unfortunately me and my Nan found ourselves in the same situation as yourself and I am STILL trying to get things sorted (my complaints to the care company started in November last year).
My point of view was that if you are paying for a service you expect to get what you are paying for and my Nan did not. We had the exact same issue as Oh Kickers, people staying for a couple of minutes and claiming they were there a full hour! I actually felt that the care company that she was using put her life in danger a couple of times and after complaints to them that they didn't take seriously I have taken things further to the Local Government Ombudsman. I'm currently waiting to hear back from them with their decision, so fingers crossed the care company do not get away with it!
Hopefully if you do what has previously been suggested and go to the manager with what you are unhappy with they will put it right unlike the ones I had the pleasure of dealing with!
If I can help at all then please just let me know
I still have a copy of my complaint I could PM you (if things get that far!)
Fingers crossed for you that you get it sorted quickly. x