Terrible ***** Pirate

This company send me sms on the 12th of July. I paid them on 17th July. On the 19th of July they send me a new bill when I ask they said I used a wrong reference after I also send them a what's of proof. Now they demand more telling me it's because the sms was sent on the 12th and I only paid the 17th no sms in between. They even tried to threatening me with lawyers. I want know why being so *****. They really are all sharks thinking that there are stones to that can make money for them