Martin WH Ng

Hello. I am a overseas landlord from Hong Kong and I have a house in UK for rent. So I need to do self assessment tax return from 2021. Recently I change my postal address in Hong Kong. And I tried update my address by setup on-line account but it's fail because I haven't got the National Insurance No. and I tried to call the telephone no +44 161 931 9070 but I wait for two hour and cannot connect to your colleague. So I want to ask: 1) Is there any other way to change my postal address? 2) Can I change my postal address by post? If yes, can you give me the right address for me to mail the change address form? 3) Finally do I need to copy any form to change my postal address?