^I think you're confusing BP and DP.
There is a huge laundry list of conditions that can trigger the requirement for a DP.
Some changes of use do not require a DP. I think you can change between various forms of retail without a permit.
Here is a good place to start.
http://lub.calgary.ca/Part2/Division...nt_Permits.htm
Calling 311 is your best bet though, as there are certain things (is it an old building sitting on a setback with no relaxation?) that can trigger DP requirements regardless of the construction scope I believe.
And most of all, if you need a DP, have fun
The amount of erroneous information that is required even for the smallest scope of DP is completely asinine.