I remember a friend of mine (now sadly deceased) answering the office phone in Welsh to a rather pompous English lady with a courteous ‘bore da’.
Even if all you do is say ‘Bore Da’ to a fellow learner in the morning, start with that.
I cant see how saying ‘bore da’ will do people in a call centre any harm.
‘Bore da, Sian!’ said grandpa.
The proceedings were entirely in Welsh, with simultaneous translation to aid people like me who can hardly say ‘good morning’ in the language (bore da).