"Mr Lingo dych chi?"
Translation:Are you Mr Lingo?
Accents in Wales can vary quite a lot from area to area.
/dach chi/ is just how dych chi is pronounced, and informally written, in parts of north and north-west Wales. You are likely to hear it as /dech chi/ in much of mid-Wales and /ych chi/ or /ŷch chi/ in parts of south Wales.