Warsaw were kicked out of the competition after they accidentally fielded an illegible player for the last two minutes of the second leg of their tie with the Scottish giants.
Now, former Rangers defender Berg has revealed his annoyance at Celtic's lack of communication over the matter.
"I called Ronny on the phone, it was a powerful conversation between us," Berg is quoted as saying by The Express.
"I was disappointed that people at Celtic could not answer emails or phone calls from our club. All they had to do was speak to us. Celtic surprised me that they could not settle the matter in a different way.
"I am convinced Ronny would have liked to have played a game so they could try and beat us on the pitch in a sporting competition. But the rest of what was said between him and me is between us. The punishment is the equivalent of forgetting to pay the electricity bill and being sentenced to 20 years behind bars."
Legia will now take their case to the Court of Arbitration for Sport.