Since Self Checkout was introduced, I have been paying for my purchases at the relevant terminal by credit card. Always without any problems, as I make very sure that the payment process is completed correctly with "OK". About three weeks ago, I received a letter from Migros. It informed me - in a very friendly manner - that a payment transaction had not been completed correctly and that I should please transfer the amount in question. Well, that can happen to me too. Yesterday, however, I received another such letter in my letterbox concerning a different purchase. The letter was accompanied by the corresponding receipt and I was not actually charged for either purchase. Naturally, I transferred the invoice amount immediately, although a payment period of 30 days is allowed. Nevertheless, I still have a bad feeling, as I can hardly believe that the mistake is mine and I don't want to risk being registered as a potential shoplifter. Has anything like this happened to anyone else? Are there any known technical problems at Migros that can lead to incorrectly completed payment transactions? I should also mention that it regularly takes several attempts at the Migros terminal before the card is recognized. Elsewhere, however, it always works straight away.