Too bad there is only one calling card available

Sign outside Dollar Prince store, Toronto, Ontario

Is it too much to ask for retail store signs to be accurate? According to this sign, found outside a Dollar Prince location, the store only has one "calling card on sale".

I'm sure there is more than one card available, but that is not what the sign says.

In the best case scenario this sort of error just annoys pedantic people like me, in the worst case bad English sends the customers elsewhere.

Customers are hard enough to find at the best of times, sending them away due to poor English is inexcusable.