A Texas repairman found that one of the hardest parts about being trapped while servicing a bank's automated teller machine was convincing customers coming for cash that he was stuck.

The ATM technician shouted and passed notes begging for help through the machine's receipt slot for about three hours on Wednesday but his appeals were mostly ignored, police said.

"Most people thought it was a joke," Corpus Christi police spokeswoman Gena Pena said on Thursday.

The man, who was not identified, left his phone in his vehicle, she said.

Since the area housing the ATM had thick walls and his voice did not carry well outside, he wrote polite notes.

"Please help. I'm stuck in here and I don't have my phone. Please call my boss," a note broadcast on Houston TV station KHOU showed. The station blocked out the number.

One customer who received a note showed it to a police officer passing by, which prompted a call to the boss and a rescue operation. The man was found uninjured, police said.

"The poor guy was just mortified," Pena said.