Tug driver reported a loss of control of aircraft after aircraft rolled into towbar during disconnect process due to a communication breakdown between pilots and tug driver.

Narrative

I was working out bound to ZZZ after completed my walk around and inspection of towbar Aircraft X then I proceeded with communicating with the pilot (red sticker inside the pushback) and was approved to push 'tail north drop point beam. I then stopped and told the pilot to set the brakes; the break light turned on and I then put the pushback in neutral and set my emergency brake. I then signaled to the right wing walker First Officer (FO) side to release the towbar. Then the pilot said to standby; the tower is asking to push back to gate. Then I told the pilot to make sure because my towbar is already disconnected. The pilot said he would call the tower to confirm the change of gate then I called my wing walker on the FO side and at this time the plane had rolled forward towards the towbar and that's when I told the pilot 3 times to set the brakes and he did. The pilot thought that I had already reattached the towbar. The aircraft moved forward and damaged the towbarSuggestions: Memo for the pilots to execute the demands or requests of the pushback driver.Cause: The pilot released the brakes without me giving him orders to release"