I have received two proforma invoices for the same service. What is happening?

Before anything else, you need to check whether it indeed concerns the same service charged on both invoices or twice on the same invoice. There is often confusion between the hosting package (space) and the domain (name). There may be two different services under the same name, and for this reason, if the due date for hosting differs from the due date for the domain, two individual proforma invoices will be issued.
If the due date is the same for both services, only one proforma will be issued. However, it can happen that two proformas are issued for one service. This is either because the service was ordered twice, or because payment in advance for the service was requested, payment on the issued proforma was not made, and the billing system automatically generated another proforma according to the initial due date of the service. In this case, it is sufficient to pay only one of the proformas and contact the sales department to cancel the other one.