Please advise as to whether an employer can change your pay periods without notification to employees. Also, if a new payroll company is hired and

Sounds like a shady pay roll company. but it is possible that if they changed pay roll companies that they could change the pay periods, if the new company has strict payout periods.

Have you brought up your concerns with your HR department?

Absolutely contacted HR, and he says he will get the last pay stub from the previous payroll company if he runs across it, which hasn't happened so I don't know when the pay period starts with the new payroll company. I talked to the new payroll company today and he provided copies of my pay stubs, but no start dates. He said he doesn't know because the HR person just calls in the hours not the date so I only get the pay period ending info. So there are no strict pay periods as we have been paid through to the 12th, 13th, 14th and the 28th, 29th, and 30/31st as the STRICE pay periods are to be paid on the 1st & 15th, but the cut offs vary.