Dropbox issue

Getting a bit frustrated with this one and wonder if anyone has cracked it. I installed dropbox a couple of years ago(free version) and within a short time is said 'exceeded allowance, dropbox full) couldn't solve it then but now I have a specific use for it and not only is it full, but in the last week it has even attracted more data! I have now '3.7gb of 3.25' In the past I deleted all my photos and anything else that looked anyway big but no help. I clearly have very little stored but it still tells me i have no space left, so it is effectively useless for a sharing group I need to work with. I have permanently deleted files. I have checked 'shared files'.  I have gone on forums where others have the same problem. I have been in e-conversation with Dropbox who are tiresome and frustrating in not ever addressing the issue directly. Cynics say they just want you to pay for content, but many people use the free version without any problems. I feel like one of those Labour Party members who have had their vote pulled without any explanation. (ok I'm stretching the analogy there...) any new ideas welcome!