Best way to create a link between two different types of users?

Background:

We have two different users: Customers and Service Providers.

Now Customers can have Service Providers and naturally, Service Providers will have Customers.

Now the Admin has the ability to create a link between Customers and Service Providers.

Problem:

I am a bit confused whether I need to create the ability to link both ways: meaning, Customers dashboard will have a "Link to Service Providers" button and vice versa, Service Providers dashboard will have a "Link to Customers".

That, versus, just creating from one side since the other side will automatically be linked anyway.

Which is better and more common?