It's best to contact the Child Maintenance Service if you're having problems receiving payments from the other parent.
The Child Maintenance Service can collect payments for you and start enforcement action against the other parent if necessary.
If there's a court order about your child contact arrangements, it's important that you don't break its terms – even if the other parent has stopped paying maintenance.
The courts will not see this as a good enough reason for a breach. They view child maintenance and child contact as two unrelated things, dealt with separately.
You could be held in contempt of court and get a fine or another penalty.