We have a customer who is not responding to payment emails and calls. I would greatly appreciate if you share any contacts / references or experience / feedback on collections for German clients
My customer's company is in Troisdorf
I'm sorry to hear you have this kind of unpleasant relationship with a client. If you're able to discern what has caused them to be non-paying, it may give you insight on how they can be motivated to pay. You can of course simply suspend service immediately and that will separate your client from the assets they were developing. It doesn't immediately solve the payment issue, but it may prompt an actual conversation. You can sell the debt to a local collections agency, but that will typically result in a very low amount of cash compared to the size of the bill. It also leaves a lasting negative impression if you believe that the relationship could be salvaged with your client.
At a minimum, you should cut off access to any resources that they hired you for until they communicate. Don't put too much effort into continued attempts. Send official-looking collection notices to indicate the bill will be turned over to collections if not paid by a specific date. And then stick to it. Hopefully you have not transferred too many more assets than you have collected for. Any mid-step work should stop so you're not creating more debt for the client.