Show Cause Letter for not attending calls

Hi Team, I work in an reputed organization and they sent me show cause letter as below, "It has been brought to our attention from ..............(HR) and that record of you for not responding to the emails sent and calls made by HR and though you have been regularly swiping in and out which is a serious disciplinary concern and violation of Company’s Code of Business Conduct and Ethics. We here by inform you that an inquiry shall be held with respect to above alleged misconduct by presiding officer Ms. ......... on at a time, through telephonic inquiry (Call) Please ensure to appear for the inquiry over the call and provide an explanation on the reported violation of Company’s Code of Business Conduct and Ethics. You may contact our representatives, ........: +. or ......... for any clarification that you may need with respect to the inquiry. Should you fail to submit the justification for the inquiry officer as required or provide an explanation, we shall be constrained to initiate an ex parte proceeding against you and take any necessary action based on the above as per the legal and compliance policies of the organization." I have missed out some calls and I mailed them that, I can't speak to those person as the last conversation I had with them - They asked me to resign which gave more anxiety leading to depression. But e-mails I have responded to all and I also have a mail proof where the HR didn't reply to my final mail sent to him. My Questions are: 1. Is it enough that I address only the issues mentioned in the letter - Since I have been in free pool for sometime they may cross question me to that? 2. Am I allowed to have a legal advisor on my behalf during this meeting? 3. I don't want to get terminated - So what is the best possible way out of this - Shall I fight or shall I quit? Kindly Advise please?