应该没办法在线改
这个我做过，当时是去的HDB Branch Office，就在家隔壁。如果你的房子是私人的，恐怕就得跑一趟cpf branch了。
staff态度不错，拿到号，一说就给办了，表格都不用自己添。

if you have taken bank loan
there is no way you could revise it online (there is an option for you to terminate CPF installment in you online CPF service though, if i am not wrong), you have to download a HBL/3 from CPF website, fill it up according and mail it to CPF board. here is the link

http://ask-us.cpf.gov.sg/hybrid/Themes/CPF/related.asp?MesId=5166805&FolderID=0&Selected=2&CSRId=&SourceId=0

if you have taken the HDB loan, you will need to go to the HDB branch (this is not referring to the toa payoh HDB hub, it refers to the HDB branch near your home) and do it at the counter.

btw, my case is a HDB flat, not sure if it would be different for private property.