Visa Inc posted better-than-expected quarterly earnings on Wednesday as the world's largest credit card network increased prices, slashed expenses and consumers used debit cards more.

Net income rose 70 percent to $536 million, or 71 cents per diluted class A share, for the second quarter ended March 31, compared with a profit of $314 million, or 39 cents per diluted share, a year earlier.

On an adjusted basis, reflecting a normalized tax rate, restructuring and purchase amortizations, quarterly net income rose 38 percent to $553 million, or 73 cents per diluted class A common share. On that basis, analysts expected earnings of 64 cents per share, according to Reuters Estimates.

Net operating revenue rose 13 percent to $1.6 billion, while total processed transactions -- which represent transactions processed by VisaNet -- increased 6 percent to 9.4 billion.

Visa said payments volume fell 1 percent for the quarter ended December 31, which translates to revenue in the following quarter.

Visa is partially insulated from the credit crisis because it processes transactions rather than lends funds. However, the company has seen a slowdown in the growth of revenue and transaction volumes as battered consumers used their credit cards less.

Still, debt-burdened consumers have been increasing the use of their debit cards.

Adjusted operating expenses fell 5 percent to $745 million, as the company cut personnel, advertising and marketing, as well as consulting fees, and administrative costs.

The company increased its forecast for its annual adjusted operating margin to the low 50 percent range from a range of the high 40 percent to the low 50 percent range.

Visa also affirmed its forecast of an annual net revenue growth of high single digits in 2009 and at the lower end of the 11 to 15 percent range in 2010.

The firm also reiterated its annual adjusted diluted class A common stock earnings per share will grow over 20 percent.

Visa shares were slightly lower after closing up 4.6 percent at $63.51 on the New York Stock Exchange. The stock is up 20 percent in 2009.

(Reporting by Juan Lagorio; Editing by Phil Berlowitz)