Update

Thank you so much. Really. I appreciate the help. 🥹

Upon reviewing my emails, I have discovered some important information regarding the situation. It appears that I did indeed acquire a prepaid card with O2, but this is not what I am currently being charged for 🙂

To provide some context, when I initially sought to have a contract instead of a prepaid card, I used a website to search for different tariffs.
I accidentally ended up creating two contracts one with O2 and another with Vodafone.
I completely forgot about the contract with O2 as I was already paying for a tariff and believed I had no additional commitments. I never used the O2 number and constantly attempted to revoke or terminate what I thought was the prepaid card contract.
I realize now that this may sound foolish, but at the time, I was overwhelmed and confused, and I genuinely did not comprehend the situation, i wish i did.

Regarding the comment made about contracts only being terminable by post, an O2 representative informed me that termination via email was also permissible.

As i previously stated have made multiple attempts to contact your law firm, including phone calls and emails, but I have not received any response whatsoever. I am at a loss as to how to proceed and whether there is any possible way to avoid paying the €700? And how bad is the situation?? How serious is it? What do I do?