Would prestadora de servicios mean service provider in the following context?
A legal and commercial relationship exists between the company and the client a través de una prestadora de servicios que factura de manera regular.
I suppose that "service provider" could work. However, it's hard to say without knowing more background information. Also, it's a little confusing when you mix English and Spanish. You should show us the complete sentence in Spanish and describe the type of text and the industry.