I’m not entirely sure if they will be able to send you an invoice that old… but you can schedule a callback and ask. Just a heads-up that there is a fee involved in sending a bill manually :)

Hi @Jacdaw 

You should be able to see the service agreements in your self serve account, please check this article and let us know if that helps https://www.koodomobile.com/en/help/viewing-and-downloading-your-customer-service-agreements-csa

Thank you for the article Flo, I have found the invoice.

I’m specifically looking for the serial number of the phone though - I thought it would be on the invoice but it’s not. It says Serial # Not Applicable
Is there a way to find the serial number of the phone I purchased in 2016.

The invoice didn't have the serial number. I believe it might have the phone IMEI on it. You could try to contact Apple directly and ask them about the serial number from the imei.