Four ways, and which one you want depends on what has gone wrong.
A ticket, from inside the panel
Open this next to the line you are asking about. The panel attaches the customer, the servers their line is on and when it expires, so nobody has to work out which of your customers you mean, and nobody has to ask you to paste a username.
That is the whole reason it is the first option. A question about one customer answered in the place that already knows about that customer is faster for everybody than the same question in a chat window.
Live chat, on this site
The chat button is on every page here. Use it when you have not got an account yet, or when the question is about buying rather than about a line: what a credit costs, whether a provider is carried, whether something is worth trying.
Telegram, at @satcable
For when it needs to be quick and it is not worth a ticket. A customer on the phone, a line that should be live and is not, that sort of thing.
info@sat-cable.com, if you would rather write it down. It is the slowest of
the four and the best for anything that needs a record: billing, an
arrangement, something you want in writing.
Where we are
The Netherlands. The servers are elsewhere and deliberately unremarkable, which is the answer to the question everybody asks next.
Before you write
Two things answer most of what arrives.
If a line is not working, look at the client view first. It says whether the customer is connected at all, and if they are, which channel they are on and whether it decoded. A line that shows connected and decoding is a receiver problem at the customer's end, and a line that shows nothing connected is usually a config file that never made it onto the box.
If a payment has not appeared, it appears by itself. Credits land on the account as soon as the payment clears. There is no code to redeem and nothing to send us, and if it has been more than a few minutes, that is worth a ticket.