He works as a collector for an electricity company. Is it permissible for him to change the currency before giving the collected money to the company?

Praise be to Allah.

Collectors for electricity companies and other representatives are entrusted with whatever money comes to them, and they have no right to dispose of it in any way other than that for which their bosses have given them permission. Allaah says (interpretation of the meaning):

“Verily, Allaah commands that you should render back the trusts to those, to whom they are due”

[al-Nisa’ 4:58]. 

What they must do is give the money to the company as they took it from the customers or subscribers. It is not permissible for them to change it from one currency to another. If they do that, then the additional amount belongs to the company, and they have no right to take anything from it. 

And Allaah knows best.