If your maintenance order was initally sought through the District Court, then this is where you will be heard again. You need to go there as soon as you can to adjust the order, however it is very unlikely you will be paying "no" maintenance despite your circumstances. Even if it is only 10 euros per week. Your children don't live on fresh air, and it shouldn't be expected that they should.
Why was your social cut? Usually for a self employed person that this would sound correct.