At Heels.com’s uptown Charlotte offices, workers ordered in pizza for lunch on Monday. With Cyber Monday in full swing, there was no time for lunch at the online women’s shoe business.

Dozens of employees with headsets sat in front of computers on the 17th floor of the NASCAR Plaza office building, talking to customers on one of the busiest online shopping days of the year.

“Today is crazy. The phones are ringing off the hook,” said Emily Denby, shoe buyer for the company. She said Heels.com, which was founded in Charlotte in 2007, was seeing three times its normal sales volume on Monday. The company was offering graduated deals, from $20 off orders of $80 to $350 off orders of $1,000 or more, to lure shoppers.

Retailers have increasingly touted their discounts on Cyber Monday, a shopping day which was started in 2005 by the National Retail Federation’s online arm, Shop.org. Their goal is to entice workers who are back at their desks following the long Thanksgiving weekend to shop.

Online sales have been growing faster than sales in brick-and-mortar stores: On Thanksgiving Day, online sales grew 32 percent over the year before, to $633 million. On Black Friday, online sales rose 26 percent, topping $1 billion for the first time.

Last year, Cyber Monday was the busiest single online shopping day for the second year in a row, with $1.25 billion in sales, according to retail sales tracking firm ComScore. That total could surpass $1.5 billion this year, ComScore said. The NRF forecast more than 129 million Americans would shop online this Monday, up from 122.8 million last year, and 85 percent of retailers were set to offer an online promotion of some kind.

Two local retailers, Belk and Lowe’s, have been beefing up their online presence as a key part of their growth strategy.

In Charlotte-based Belk’s massive online order fulfillment center in Pineville, workers moved between huge rows of shelves Monday, picking goods from boxes and packaging them up to send to customers. The company offered online specials, such as 50 to 60 percent off women’s boots and free shipping on all orders.

“We’ve had a great day with e-com(merce). We’ve seen very strong sales,” said Belk spokeswoman Jessica Graham. She said Belk’s sales surpassed those on Cyber Monday last year.

Mooresville-based Lowe’s offered Cyber Monday specials, including an Iris home monitoring and security system marked down to $149 from $179, and a Skil miter saw for $79, marked down from $119. Company spokespersons didn’t respond to a question about the company’s online performance Monday.

Retailers are coming off a fairly strong Black Friday weekend. Sales from Thanksgiving through Saturday increased 13 percent, to more than $59 billion.

Big retailers score sales

Much of the Cyber Monday spending goes to large companies. Experian Marketing Services said Monday that the five retailers getting the most online traffic were Wal-Mart, Best Buy, Amazon, Sears, and Target – all with prominent, heavily promoted discounts.

But other less traditional Cyber Monday retailers also tried to get in on the act. The Billy Graham Library in Charlotte offered specials such as a Bible that normally sells for $14.99 on sale for $6.99. Tennessee-based Dollar General debuted a new mobile app for online sales, such as a $10 Polaroid MP3 player. And Gander Mountain, the outdoor and hunting supply store, offered a free $25 gift card with the purchase of a new firearm online.

Online commerce is expected to continue growing quickly. In Heels.com’s office overlooking Charlotte, Denby detailed some of the advantages she sees: Less hassle, no crowds to fight, no lines.

“The Internet is everything these days,” said Denby. “It’s going to keep growing because it’s so convenient.”