Access to old IPhone 5

I sold my company and as part of the sale kept the small assets etc (computers, laptops, phones etc) that were of no use to the new buyers.

I have a old IPhone 5 that was purchased by the company, but have no access to the phone as the Apple ID is associated with the person for whom I used it for (programme manager) and the company I no longer own.

'name.name'@'company.com'

I can show that I was the owner of the company to proove ownership, but that only assumes the phone is known to Apple as being linked to the company.

In short, without the Apple ID how can I access a phone I own (old as it is) without the Apple ID please?