Looking for an ABA company in SD County that accepts FFS medi-cal ('straight medi-cal) - not a medi-cal HMO

Hi all, I'm looking for an ABA company to work with my kiddo with autism and I'm getting the run around from everyone. Regional Center says to contact PCP for a referral. PCP says to call medi-cal. Medi-cal says to contact Regional Center. ABA companies say they only work with specific medi-cal HMOs and that my child "must have been assigned to an HMO" but he hasn't. Guidance would be so appreciated, even from those from out of SD County that have experience with navigating ABA with FFS medi-cal. TIA.