In short: disputing a card payment (chargeback) is asking your bank to return money paid with your card when you did not authorise the payment, it was wrong, or the amount was higher than expected.
Simply put: Write to your bank with evidence: statement, receipts, messages. The law gives clear rights for unauthorised payments and for payments without an exact amount, such as a hotel block. Card schemes have their own dispute rules too, for example for goods not received; terms and deadlines are in your bank contract (*).
Example: A hotel charges you €180 instead of the agreed €120. You write to your bank within 8 weeks and attach the booking confirmation.
Watch out: in a dispute about the quality of goods, talk to the merchant first; a chargeback does not replace your consumer rights.
EU rule: if an amount authorised without an exact figure exceeds what you could reasonably expect, ask for a refund within 8 weeks (Directive (EU) 2015/2366, Articles 76–77).
Example: Bulgaria — the deadline is 56 days and the bank answers within 10 working days (Payment Services and Payment Systems Act, Article 82(2)–(3)). If you are not satisfied — the Conciliation Committee for Payment Disputes at the Consumer Protection Commission (CPC), free of charge.
Check in your country — the out-of-court body for payment disputes: https://consumer-redress.ec.europa.eu
Source: Directive (EU) 2015/2366, Articles 76–77: https://eur-lex.europa.eu/eli/dir/2015/2366/oj · Payment Services and Payment Systems Act (in Bulgarian): https://lex.bg/laws/ldoc/2137182267