Unfortunately you’ve been lied to. Since 2015 Berlin taxis (note this doesn’t apply to the rest of Germany) are required by law to accept EC cards and at least

Unfortunately you’ve been lied to. Since 2015 Berlin taxis (note this doesn’t apply to the rest of Germany) are required by law to accept EC cards and at least 3 different credit card networks (which in practice means Visa, MasterCard and AmEx). If the reader is not operational they‘re comitting a misdemeanor. Best advice is to not pay and ask them call the police if disagree - usually the machines magically start working again. Why are the drivers lying about it? The fee they‘re paying is relatively high (about 3%, but it‘s somewhat offset by a 1.50€ surcharge) but more commonly they‘re are either trying to avoid taxes and they‘re using someone’s taxi without holding a license themselves.