Unionized workers at Reliance Home Comfort were rallying at the company's Burlington headquarters Wednesday.
They're demanding their employer end the month-long lock out of 800 workers, including 28 workers in Sarnia and seven in Chatham-Kent.
Unifor National President Jerry Dias is asking customers to give someone else their business until a deal is reached.
"We are escalating the campaign to encourage customers to take their business elsewhere as long as this greedy employer refuses to come to negotiate an end to this lockout," said Dias.
Unifor Local 1999 represents HVAC service technicians, installers, water heater installers, plumbers, electricians, and administration staff, have been locked out of 13 locations across the province since May 13.