I can tell you what probably happened. They didn't want to accept a card payment because that would have to go through the books. Cash payments are much easier to disguise. Plus, they may have needed cash to pay a supplier later that day. That doesn't excuse what is appalling behaviour but those are the likely scenarios. Don't ask how I know ;-)

Playing devils advocate here - but what if they misheard what the owners had said and thought they accepted credit cards when in fact they didn't? Could have happened easily couldn't it? Then it would have been a simple misunderstanding.
Won't ask you how you know about cash payments tony!

Er no not judging but making a point that the OP's experience is so outdated and that the B&B clearly state in their website they now accept cards.
I'm just reading the op again. I am confused now what the relevance to the internet connection is if they weren't going to accept credit cards anyway.
As bellart said, playing devils advocate could their internet connection be down for a while and they thought that you had recently made the booking? If they thought it was recent perhaps they figured they had told you.
Who knows.
OP. As you've gone to all the trouble of registering simply to make a complaint about something that happened 15 months ago, you give the impression of being just another "one-post wonder with an agenda". Maybe you did have a bad experience. But you might also run the B&B next door. Who knows?
You want TripAdvisor for your unsubstiated whine. You'll get more sympathy over there.
People round here tend to be a bit more sceptical.

Good point, morag.
Just another thought - maybe because it was reviewed in Lonely Planet, that the OP thought this was a good place to complain?

Have done a little research after Morag suggested Trip Advisor, I had a quick peek myself.
What a mixed bag of reviews! Some were very good but overall I think there were more complaints than praise. What is particualrly interesting though, that at least 3 or 4 (out of 26 I skimmed) said they had been told they accepted credit cards and then on departure told only cash....
If I'd read these reviews, I would have been very sceptical about the place and probably wouldn't have booked a stay - there were just too many negative comments for my liking.
But you might also run the B&B next door. Who knows? You want TripAdvisor for your unsubstiated whine
Morag, if you read the recent press reports and travel industry misgivings about Trip Advisor, that is exactly where the people who own the B&B next door post their 'reviews'. I wouldn't trust Trip Advisor reviews on accommodation any further than I can throw my neighbour's donkey. I used to trust them, but not any more.

Point taken tony, but also in this case, why didn't the owners respond to the complaints that people had made about being suddenly told to pay cash, when they had responded to other complaints about the rooms etc? They could have easily put the record straight by saying that was simply untrue but they didn't - weird!