Air carrier Tug Driver reported the Captain released the brake without clearance or notifying ground crew reportedly due to headset communication issues. The aircraft rolled back upon chock removal prior to departure.

Narrative

After working the flight; Ramp was ready for pushback. I was trying to call to flight crew on the headset but no answer; I waited a few minutes tried again still no answer. A few minutes later I saw the plane roll back while my Wing Walker was by the nose gear and there was a green light showing the brake was released. I then got the attention of the pilot - he put his headset and I asked him why he released the brake without clearance. He said he'll put back on; I told him that he need clearance to release the brake because I have a Wing Walker by the nose gear wait to capture; He then tells me so you want to play that game" then took off his headset. So I contacted the Gate Controller to inform them what was going. A few moments later the Gate Controller called me and told me the crew was ready. I went back outside I put on the headset and heard the First Officer say "Screw this place." I told the crew we were ready; they released the brake; we captured the plane. We then were cleared to push. Almost completing the push I told the crew they were clear to start; no response. When I got to the stop mark I told the crew to set brake; no response. I tried to communicate with the crew but no response. So I then started to pull the plane back in the gate; halfway in the gate the Captain asked what going on. I told him I was trying to call him and didn't get a response so I was going to get a new headset; he said he didn't hear anything. I got a new headset; we pushed the plane out again. After disconnecting from the plane I showed the strap and my Wing Walker waved them off looking at them eye to eye. We returned to the break room and the Gate Controller called and said I didn't show the strap or get a salute and wouldn't leave. To me it was the Captain "playing games;" because it is not required to show the strap or salute. But most importantly the Captain did NOT follow SOP by releasing the brake that could have caused serious injury or worse.Second time today on Gate XX. The Captain released the brake without clearance and without any notification. Prior to departure I was removing the chock from the front nose gear and the plane rolled back. Then I look at the light on the nose gear and the light was green. Tried to contact the flight crew via headset but the crew didn't have them on."