A Harvard University professor started an email war with a bartender at a Chinese restaurant over a $4 overcharge.

Benjamin G. Edelman, an attorney and associate professor at Harvard Business School, ordered takeout last Friday from the website menu of the Sichuan Garden restaurant in Brookline, Massachusetts, Boston.com reported. But upon receiving his bill, he noticed all four items he ordered cost $1 more on the online menu.

Edelman emailed the restaurant. The bartender who runs the family-owned business, Ran Duan, replied their website prices have been outdated for a while.

Duan offered to email him the correct menu and said the website would be updated, Boston.com reported.

Unsatisfied with the reply, Edelman responded, "Under Massachusetts law it turns out to be a serious violation to advertise one price and charge a different price."

The professor demanded he be refunded $12, or three times the overcharge amount, in accordance with state law.

Duan said they can only afford to refund him the original overcharge, an offer that apparently set Edelman off because his next email revealed he already contacted the "applicable authorities" to make the restaurant provide refunds to all other customers they overcharged.

"It strikes me that merely providing a refund to a single customer would be an exceptionally light sanction for the violation that has occurred," Edelman wrote, according to the news site.

"To wit, your restaurant overcharged all customers who viewed the web site and placed a telephone order...You did so knowingly, knowing that your web site was out of date and that consumers would see it and rely on it," wrote the professor, who graduated summa cum laude from Harvard College.

The email spat continued, with Edelman eventually demanding he be refunded half of his $57.35 bill. Duan agreed, provided the proper authorities get involved.

Brookline town authorities told Edelman "they wouldn't be able to help," Edelman told The Boston Globe.

After the email exchange went viral, Edelman apologized for the incident on his website.

"I aspire to act with great respect and humility in dealing with others, no matter what the situation," he wrote. "Clearly I failed to do so. I am sorry, and I intend to do better in the future."