The phone company is required by law to back those records up and store them. The only question: How long?
You say "certainly exist" and then you admit you don't even know how long they are kept. Do you know what "certainly" means?
Call your cell company and ask and then tell me they are kept for 8 or 9 years.
I'm not so sure. A bill collector from India started hassling a relative of mine last year about a small, supposedly unpaid AT&T bill from 1999. When we called AT&T to get proof that that the final bill had been paid earlier that year, the representative we spoke to made it sound like they don't have records that go back even that far.