Probably not the usual question and will need moderator assistance.
Back in April was having broadband issues and was sent out a replacement SH3, before it arrived the existing modem started working normally again and the replacement is still in the sealed box. Got an email requesting a return today and there is a serial number quoted in the email, but this may be the old one.
Presumably that will cause an issue if I return a SH3 with a different serial number.