The robbery happened around 11:00 a.m. at the T-Mobile in the Penn Mart Shopping Center.
Delaware state police say Campbell entered the store armed with a handgun and confronted two female employees.
Campbell allegedly pointed the gun at the women and demanded money. The victims complied and turned over an undisclosed amount of cash to him.
The suspect then fled on foot. There were no reports of injuries to the two employees, both in their 20's who were in the store.
Police say Campbell was arrested at his residence Tuesday and charged with two counts of robbery 1st degree and two counts of possession of a firearm.
He was committed to the Young Correctional Institute on $202,500 cash bond.