Account Over Disk Quota

Every time a customer sends a form in, we are getting a message with it saying “your account is currently over disk cults. Form submissions can not be added to…..” and then it lists the url for which ever form they filled out. The customer is then getting an error on their end saying it could not be submitted and to try again. And they do. And submit it again. And sometimes they are trying a 3rd and 4th time. As fas as we can tell, we are getting the web submissions bc we are receiving multiple copies of their forms. This is a huge problem for our customers as they are duplicating work. It’s a huge cost to us bc our emails are set to auto print - so we are wasting a lot of paper and toner. 
We should be no where near our disk quota. Can someone please advise as to what we should do?? 

I swear we have different issues every week with Homestead. It’s getting old and very frustrating. 

Thank you!!