Dear manager,
Thank you so much for discussing my work situation with A and B. Four days WFH in a week, indeed, is a good offer. I wish this offer have had provided before I decided to move on. I have already accepted the offer from XXX, with regrt, I would like to resign my position in XXX. My last day is XXX.
Sincerely Yours,
IIyyy
這件事兒你已經贏了,就寬宏大量一點兒,給你的管理和A部門的領導留個好印象。山不轉水轉,沒必要燒橋。