When to use capitals

Please can you tell me which or the following is correct?
Please do not hesitate to contact your Account Manager............
or
Please do not hesitate to contact your account manager.
The Account Manager being a person/thing.
I would appreciate your help here.
Kind regards

[me78]

account manager is a person in a organisation, but I am not sure whether it is informal to whrite it in this way "acount manager"

[mykwyner]

In this case, account manager is a common noun and would not be capitalized.