receiving email addressed to another email address

I don't know how they're being sent to my email address

One possibility is that you have been BCCd (Blind Carbon Copied) as a recipient and the from address is forged (this is trivial to do).

Spammers will try all kinds of tricks to get their email to land in your inbox.

You should just ignore these emails (unless you are expecting to receive them from somebody you know).

they're mostly spam emails and i unsubscribe from them

That's pretty much a waste of time for you (unless the mail is from a reputable source, like a website you have an account with).

i've been entering my westnet email address

The downside is you have now confirmed your westnet email address as a valid address to the spammer. You can now expect even more spam.