I am a material supplier on a job here in Texas. We provided ready mix concrete on a job, our customer was a sub contractor. The GC and Owner are the same entity. I have only been paid about half of the $20,645.28 that I am owed on the project. The Owner/GC has paid the sub (my customer) and he signed a lien waiver. I sent them the monthly notice but just received an email from them stating they are disputing it because they paid the subcontracor. My question is, is the lien still valid since I have no been paid and did not sign a waiver?