An elderly US man who worked at the same toll booth for almost 30 years has been sacked for reportedly helping a motorist pay his fare with his own money.

Vladislav 'Sam' Samsonov, 77, was working as a toll collector on the Boca Grande Causeway in Florida until being fired last week, WBBH reports .

After realising he had charged a truck driver too little, he paid the outstanding $5.50 out of his own pocket, something he had done a number of times during his 29-year stint in the booth.

"In my eyes there was no crime committed, I just helped somebody out," Mr Samsonov said.

"I'd put the six dollars in, I got the six dollars back the next day.

When Mr Samsonov's employers Gasparilla Island Bridge Authority found out, he was told his shifts were being reduced from five days a week to just two.

When he challenged the demotion, he was shown the door.

"If I can’t be trusted for five days, how can I be trusted for two days?" Mr Samsonov said.

Mr Samsonov said he is looking at taking legal action, while locals have set up a Facebook page to demand his reinstatement.