i have stupid hardphone, proxy, registrer server is always domain :/

I have configured DNS and ser to use some domain.com as sip domain, but proxy have sip.mydomain.com addres. Registering is no problem because i can tell what domain ser should search but problem is for examplke with aliases i don't want write every time `serctl alias add user@domain.com` `serctl alias add user@sip.domain.com`

if (uri=~".*sip.my.domain.com") { rewritehost("my.somain.com"; } don't work becaus it rewrites requested uri

i hope you get my point. Any one know how to solve this problem?