yes. write a letter to tell them that to close the loop.
不能打电话,必须要写信吗?
如果是的,需要以我父母的名义写信从中国寄给移民局吗?谢谢!
yes you can try calling first. you can fax them. but it's always good to leave a paper record on the file.
if it were me i would just write the letter as myself to inform them that my parents have returned to china in time therefore will not go for the physical check up as required.