to be really mad with credit card company for taking away my lower interest rate and replacing with a very high one because I was a week late with monthly repayment...

[Trix11]

Im furious this is going to cost me an extra £50.00 a month - I phoned them to try and reason with them as it was a one off and all monthly payments are always paid on time usually.

why don't you switch to a new company with a zero % interest rate?

Well...a little bit.....you can be cross but at the end of the day the credit card company are there to make money and they will 'punish' latepayers however they see fit! Transfer the balance to another card ASAP?

If you have been with them a long time and never been late before you may well be able to get them to back down. If you can afford to pay off the balance then threaten to close your account with them.

don't get mad, get even - switch!

You can be furious, and they are being unreasonable ... but being unreasonable is exactly how they earn their profits. It isn't free credit.

That said, just switch your company, as others have said.