Over-charging is actually very common, and then it's up to you to notice, then fill many forms (last time I had this problem I had to fill over 10 forms) and then personally visit their branch, and then wait months to get your money back. It's much better to pay by permanent payment order (automatic payment e.g. every month).
SEPA (European) direct debit payments can be reversed with about two clicks in your online banking environment. No questions asked. I believe you have three months to do that, or even longer if the company doesn't have your handsigned signature approving direct debit.
Of course, the company on the other side may not be happy, and may be sending you bills and threats. But that's no different when refusing to pay without direct debit. And yes, it's up to you to notice any errors. I haven't heard of any cases of outright fraud using this system, though it probably happens.
