I think there's slightly more complexity than mdpc suggests. The letter is true: only the person to whom the relevant chunk of PTR space has been delegated can manage the PTR records in that space.
In the second paragraph they have made the assumption that the current delegate is the person who is responsible for the PA IP address space. That is usually a safe assumption, because the general structure of PTR records is such that they were delegated in chunks corresponding to the
/24 IP address block they were in. But as mdpc points out, RFC 2317 introduced a mechanism for delegating subsections of those basic chunks. I have worked with organisations who have used that mechanism to get control of the PTRs for their sub-
/24 netblocks. But it requires a highly clueful ISP, and a friendly and compliant one to boot; it is not, in my experience, commonly used.
You can walk the DNS tree yourself to see to whom your PTR space has been delegated, it is likely to be your current ISP, and not likely to be your current DNS provider, unless those happen to be the same person. You can then contact them to request either direct insertion of PTR records, or the delegation of your subsection to you or your representative.