“Advise” vs “advice”
I've seen twice in in 30 minutes how someone had said that they wanted advise on [...] subject, or how they needed advise on [...].
Is this correct?
In both American and British English, 'advice' is the noun and 'advise' is the verb. Both your examples are incorrect, because they use 'advise' as a noun. It would be correct to say "I want/need to be advised on X" or "I want/need advice on X".
Aside from the issue of advise vs advice (a Verb form vs. a noun form), there is also an issue of verb-agreement:
"I've seen twice in in 30 minutes how someone had said that they wanted on advise on [ ] subject, or how they needed advise on"
How someone had said is incorrect. Instead, it should be has said.