Write a letter to withdraw the Resignation letter.
I realise that various processes are now under way for me to leave the organization since I resigned on (date). However, due to various circumstances (include reasons) and my own change of heart, if possible, I would like to withdraw my resignation.
I hope that I can continue in my job as normal, although I appreciate matters may not be that simple, and I await your response. Thank you in anticipation of your understanding and apologise for any inconvenience I may have caused.