Recently, I've been going through some old accounts of mine (on online websites) and I started deleting them. Thanks to GDPR, this is now much easier.
Most companies' customer services have no problems with this; but I have encountered one where they were rather less cooperative. First they said that I can only deactivate my account, but I want to delete it (and Article 17 of the GDPR gives me this right).
Therefore, I further emphasised that my wish is for them to completely delete my account. To this they responded that I have to send them my passport and ID to prove that I am an EU citizen. I understand that they may have this right - but do they actually? I cannot find anywhere online that I have to do so - and actually, sending in photos of my documents seems a bit iffy to me, at the very least.