I just received a phone call from a collection agency wanting me to pay a debt from over seven years ago. Is this valid and what are my rights? They have never notified me in writing and I received this phone call in my place of employment?

It depends, the debt might be 7 years old but when was the last time you made a payment (or even agreed to pay something)

A 7 year old debt is too old for them to sue you but they can still call and ask for the money. If however you made a payment 2 years ago then the debt is only 2 years old and they can still sue.

In all cases they are allowed to call your home but not you work, send a registered letter to this company asking them to only contact you at home and do not agree to pay anything.