Have you checked for frequency compatibility of your G5 device with Telus tower frequencies? https://www.frequencycheck.com/brands/lg?utf8=%E2%9C%93&q%5Bfull_name_cont%5D=G5&commit=Searchhttps://www.frequencycheck.com/carriers/telus-canada
Your phone model shouldn't matter if the password reset works. Try logging in from a secure computer and reset the password that way. If it still doesn't work, try contacting @CS_Agent via private message to see if there's malicious activity with you...
As far as I know, only selected vendors with established locations are selling Public Mobile sim-cards. The sims themselves are $10 and then there's the additional plan prices. If the "voucher" doesn't work , in all likelihood you got scammed. Don't ...