Greenwood made mistakes with about 1,200 stormwater utility bills this week but already has corrected the errors.
The city mistakenly gave twice as much credit for payments received Sept. 14 and failed to credit payments received Sept. 17. But workers have credited all payments received and removed any double credits, controller Adam Stone said.
About 300 residents called to complain Monday, and the city returned every message, Stone said. Greenwood also will send out letters to all the affected customers, explaining what happened.
He said any mistakes will be corrected in the November bills.
The city established the new stormwater utility earlier this year in an effort to comply with federal regulations. The utility charges residents $5 a month to help keep natural waterways clean and to work to minimize flooding.