I’ve reread the OP and believe that you are not going to find satisfaction by requesting a repair. Kobo doesn’t repair. Prior to their repairability marketing push with the last three ereaders released just this past Spring, Kobo ereaders rolled off the assembly line as disposable goods.
I recommend that you:
Be sweet as honey. If you were already sweet, be even sweeter.
Have your receipt in hand. Be prepared beforehand to email them a copy.
Don’t mention repair. Save that for a separate phone call/complaint.
Write their name down for later reference if things don’t go well, or if things go amazingly, and you want to send them flowers.
Request a replacement under warranty terms. This is where your battle will be.
If you get a pedantic/patronizing/pompous CS rep who is unhelpful, and you don’t want to hang up and try again, politely request “escalation”. They’ll pass you up the chain to somebody with greater authority. If you call during regular business hours, you sometimes get them on the phone, but more often via email.
In my long history with Kobo, I believe I have had three outright replacements. That warranty is gold when things go wrong. Good luck!