What are my legal rights against a care agency for fraud and inconsistency in their services for my mom who has dementia?

Do you have documentation regarding fraud and inconsistency? If it is mom just telling you - it could be her dementia.
My experience: when I went to leave my daddy in a home I was told there would be a night nurse and a day nurse with two on each shift. So I agreed, signed the contract. I was one that wanted to meet each nurse, caretaker and make sure they knew they could call me if ever he gave them a problem - because he was 6'2" and willful! So the first day, I visited with my dad and then as the afternoon turned into evening, I asked where is the night shift? The day shift nurse said to me "I am the only one here no one will come and help me or take over" I was shocked. I immediately called the social worker and cancelled the contract because the contract said four caretakers! That night I left him there and was back the next morning with the SW and we found a new place that lived up to what was on the contract. I always checked in with the nurses/caretakers and we had a friendship so they knew they could count on me and I could faithfully leave my daddy with them.

Please provide more details.
If not, do discuss with attorney in your area. He/she will quickly let you know if you have a case.

An attorney licensed in that state is the only professional who should be giving you advice. You will need evidence for them to review. They will decide if you have a case. And if you do, and lose, you may be liable to pay for the other party's legal fees.