Cannot connect to my O2 account abroad to cancel my pre-paid data loop

Hello team,

I have bought a prepaid sim card while travelling in Germany last month. I have added a data subscription that I would now like to cancel. However, I am not in Germany anymore and it is impossible to connect to my O2 account with my email / phone number. It tells me that my account is not created, but it is since I could log in before. The only other solution is to connect with a sms code, unfortunately the sim card is not capable of connecting to any network in the country where I am (Singapore), meaning I cannot get the access code.

Could you please advise how I could connect to my account with your help so that I can cancel the subscription on time?

Thank you!