Hi
My daughter has had her A7 since December last year so it's been working fine for 7 months now.
So yesterday because of it running the battery down completely and wouldnt charge - I opened the back of the phone, took the battery out, reinstated the battery, charged the phone - now there's no sound for music or alarms or ringtones or media
You can hear someone talking on the phone but none of the above
I've checked the sound setting are on and on 100%
I've checked that it's not on flight mode or privacy mode and the do not disturb is not on

Any other suggestions please?

Before sending it back to your seller to have it repaired/replaced under warranty, i would do a factory reset just to be sure about the nature (hardware or software) of the issue.