Air conditioning

[J&K]

I know not many people come to the forum now but hopefully someone can offer advice.

Our air conditioning units are over 15 years old now and we are concerned about the safety of them. We are wanting a full service and filters chaged (4 units in total) I'm just waiting on a response from FN, but does anyone know of a reliable company that could do it if FN can't ? Has anyone else had theirs serviced?
Thanks in advance