Lane Garrison -- I Did NOT Beat My Playmate GF Ashley Mattingly

Lane Garrison insists ... he did NOT beat his Playmate girlfriend Monday night during a heated argument -- telling TMZ Live, cops were called to the couple's L.A. apartment over a massive misunderstanding.

TMZ broke the story -- someone in Lane's apartment complex dialed 911, reporting a domestic violence incident in Lane's apartment. Police showed up, but no one was arrested.

Now, Lane says whoever called 911 jumped the gun -- because Lane never laid a hand on his GF Ashley Mattingly ... and she didn't touch him either.

According to Lane, the couple had been fighting loudly -- Ashley was upset Lane was invited to her ex-boyfriend's funeral and she was not. Lane believes the volume of the argument is what prompted the neighbor to call 911.