PITTSBURGH -- Many consumers are getting a big surprise when they get their credit card bills.

Several credit card issuers and stores are raising interest rates and reducing limits on credit cards.

In many cases it’s even happening to customers with good payment histories. And it’s all legal.

Most credit card companies send notices of changes in credit limits in the mail. That is why consumers should open any mail from the credit card companies. Don't assume it is junk mail.

How many credit cards should you own?

According to the Federal Reserve about 65 percent of banks tightened their lending standards on credit card loans in July up 30 percent over April.

When a company lowers your credit limit it can affect your credit score.

That’s because when a customer’s available credit goes down it brings the current balance closer to the available credit limit and that can lower your credit score.

Credit card companies like to see customers only use 30 percent of available credit.

If you have a limit of $1,000 you need to keep the balance below $300 or 30 percent.

To make sure your credit score isn’t hurt keep track of your credit to debt ratio.

And the best way to do that is to calculate all your debt and credit limits.

Credit to debt calculator

And if you have cards that haven’t been used for a long time, keep them active don’t cancel them.

Canceling credit cards that are in good standing can shrink the amount of your available credit and make it look like your using more of your available credit than you are.

Use the cards once every six months even if it’s only for $3 and then pay it in full when the bill comes due.

And don’t be temped to open store credit cards to get a discount. That can also be a red flag to creditors. If a creditor sees someone opening several accounts at the same creditors may wonder why the person suddenly needs all that credit.