MMDVM <> XLX - Prefix


I have a link setup between a BM TG and an XLX server..      BMTG<>MMDVM<>MMDVM<>XLX

Callsigns are appearing in the the XLX dashboard, but is there anyway to add a Prefix so that it shows the callsign is coming from the BM TG ? 

I tried adding a suffix in the ini files..  but no luck so far

Many Thanks