The main issue I have is how they use your contact details.

CareerOne does not give you the option to control what kind of mail they send you in their accounts page, which meant I kept getting unwanted communication from them that periodically filled my inbox.

This was why I closed my account. Not long after, CareerOne used my mobile number to contact me to try and 'personally assist me', despite the fact that closing my account should mean that I don't want to have anything else to do with them anymore.

My advice is to use a disposable email and number when applying for this site that you can get rid of after you're done with it. It's possible that they retain your details after the closure of your account that they can use in ways that you don't intend.