Collectors only work based on loan contract.
If there is problem with loan contract or invioce, etc. they "don't care".
a typical example if medical charge collection. Usually medical charge is a mess. There is patient, insurance company, doctor office, hospital and collectors. There can be a lot of mistakes. So when credut bureau design the credit score model, they ususally ignore the medical collection records that are less than $200.
However, the collect agents (espcially those who buy bad loans to collect) usually don't spend time to investigate the claim is valid or not.
So this can bring a lot of trouble to people.
Also, even if the banks or collector made mistakes and mess up with your credit record, usually it is your responsibility to call credit bureau and ask them to fix the problem. Usually, we think it should be the party who messed it up to fix the problem. However, even if it is their responsibility to fix the problem, it may take months or even years to fix it. It is for your own benefit to fix the mistake in your credit report ASAP. To do it, you need to: 1. pull your credit report from 3 major credit bureaus and carefully exam the problems. 2. call the bank/collect and ask them to stop wrong collection. 3. call credit bureau and ask them to corrrect the mistake.
That maybe the reason ID theft is a real headache to everyone.
Sure, you can sure them, but it takes years. In 2004 or 2005, TransUnion lost a case to a lady in CA and paid $100 Million.