How to modify detail callout shape after it is placed

Our project is well underway, we have placed several detail callouts for enlarged partial plans. The client requests for the detail callout symbol to have rounded corners.  How can we modify each detail callout (all ready placed) to have rounded corners??

Partial Plan workflow - All detail callouts have been placed created on the SHEETS, which then creates a SAVED VIEW  to our composition model, which we then create a DRAWING file from that SAVED VIEW.

Using AECOsim V8i SS6