During the spring and summer months, credit card issuers have been doing what they won’t be able to do six months from now: boosting rates charged on existing credit card balances and new purchases.

A new federal law restricts new rate increases on existing card balances and modifies a number of other costly bank practices.

The banks, which need to make all such changes no later than Feb. 22, are shoring up revenue while the getting is still good. Posing as potential new customers and checking with bank Web sites and services, surveyors representing the nonprofit group Consumer Action learned that several months ahead of the law’s effective date, major banks had made all of the following changes:

-Bank of America (Stock Quote: BAC) added 3.25% to its minimum APR for purchases on its variable-rate Platinum Plus Visa card, taking its lowest rate of 6.99% to 10.24%.

TST Recommends

Inside Eli Lilly's Surging Stock Price

Lilly Gets FDA Breakthrough Status for Alzheimer's Drug

Eli Lilly received FDA breakthrough status for its donanemab Alzheimer's drug, speeding the agency's review of the product. The shares are higher.

Bed Bath & Beyond is putting some stores to sleep.

Bed Bath & Beyond Leaps on Bank of America Upgrade, Fading 'Meme' Interest

BofA analyst Curtis Nagle says Bed Bath & Beyond shares are trading closer to their pre 'meme mania' levels, and represent good retail sector value.

-Capital One (Stock Quote: COF) increased its penalty rate for missed payments or other defaults by 6.25%, bringing the interest rate to 29.4% on its variable-rate Standard Platinum and No Hassle Miles cards.

-Citibank (Stock Quote: C) has increased purchase APRs on three variable-rate cards surveyed (Platinum Select Master Card, Diamond Preferred Rewards and AT&T Universal Savings) by between 2.25% and 3.25%.

Some issuers are hiking rates across the board while others are raising rates and adjusting terms for specific customers, observes Linda Sherry, director of Consumer Action's Washington office. Sherry said that while many banks implemented increases shortly before the Credit CARD Act of 2009 was signed, other institutions including Bank of America, Capital One, Citibank, US Bank and Wells Fargo (Stock Quote: WFC) continued raising rates in May and June when Consumer Action finalized its findings.

To prevent getting stuck with a higher APR before the new law prohibits increases on all existing, fixed-rate card balances, and prevents banks from making “marginal” increases (which venture beyond changes in the prime rate) on preexisting variable-rate balances, here are a few pointers:

1. Check your balance as a percentage of your overall unused credit when deciding whether to accept a cutoff of card privileges going forward. Banks are increasingly offering an 'opt out' whereby cardholders can hold on to their original APR to pay off balances while their card gets frozen for new purchases going forward. But opting out may seriously damage your FICO score, observes John Ulzheimer, president of consumer education for Credit.com, an online resource for cardholders seeking out the best credit card deals.

2. Try to have several cards in your arsenal so that if one bank sticks you with a double digit APR, you can switch the entire card balance to another card.

3. Now more than ever, persistence pays. The new law says that by Aug. 20, card issuers must notify consumers of APR increases at least 45 days before they go into effect. If there’s been a change or late fee, call your bank and politely let them know you are unhappy. Should the representative refuse to undo your penalty or reduce a rate that has been increased, ask for a supervisor. If that doesn't help, hang up and call back later.

Related Links

How New Credit Card Rules Affect You

4 New Rules That Matter to Your Credit Score

Surprise Credit Card Cancellations: Are you At Risk?

—For the best rates on loans, bank accounts and credit cards, enter your ZIP code at BankingMyWay.com.