Daughter texted from friends house she's in which is old that her phone was being charged and its now not working properly the charge went to 78% in a minute.i think it may have been a short circuit.
Question is will o2 repair it free or will she have to pay?
Thank you in advance.

It could be a faulty charger....

Just go through the warranty or insurance process and see what happens. Don't tell them what you think it is, just tell them the facts....you charged the phone, it went to 78% and then stopped working.

Unless your a qualified electrician and have tested the house circuits how are you to know

I'll get her to check that out,thanks.