Raiders broke into the South Street shop in Dewsbury at around 10.30pm on Friday.
The outlet, which is part of an award-winning franchise, is offering a £1,000 reward for information which leads to a criminal conviction.
Marketing manager Habib Khatib warned people to be on their guard if they offered new phones or tablets for a knock-down price.
“If anybody does get offered them, we would ask them to call the police,” said Mr Khatib.
“There will be no benefit in buying them as they will soon be blocked anyway. We want people to be vigilant.”
Mr Khatib also called on people to come forward with information to prevent other businesses being hit.
“The guys who have done this are probably professionals,” he added.
“If these things continue it could have a detrimental effect on Dewsbury as investors will start running away.”
The store is open as normal today.