Sony & MyXperia - extremely dissatisfied!

I received a new Sony Xperia in July. When connecting to the computer, you receive an invitation to register on an online platform called MyXperia. This promises that, should your mobile phone be lost or ******, you will be able to trace the handset, erase all personal data and lock the handset via this online platform. I therefore registered. <br> <br> Yesterday, my handset's microphone started giving me problems, and after googling this, I did a factory reset on my handset. However, upon rebooting the telephone, I was taken to the MyXperia authentication page, which, hypothetically, links to your google credentials. The catch is, it only uses the credentials that were active on the date of registration on MyXperia. When prompted to recover these details via google, one is only able to create new login details, and not retrieve the old ones. The MyXperia then refuses to accept these details. I followed all the tips I could find online, but nothing worked. I was forced to send my handset in for repairs, with a turnaround of about 21 days, with nothing to use now. In order to use my number on another handset, I will have to pay extra for a sim swop (my old handset cannot use a nano sim).