If you are a wholesale communications supplier and you are making supplies to other service carriers or network operators to supply users such as consumers then your VAT invoices are affected by the reverse charge.
This guidance issued by the UK government involves in detail how the reverse charge is applied, how the reverse charge is applied for multiple supplies within and out of reverse charge, as well as invoicing.
Regarding Sales list, companies do not need to complete a reverse charge sales list for supplies within the telecommunications services VAT reverse charge.
Source: Gov.uk
General info on VAT after Brexit