PTR records (pointer records) point IPs to a name. Only the organization that is responsible for resolution for these IPs can do the PTRs (unless they delegate that authority to someone else -- not common).
For example, I picked a random IP (18.104.22.168) and did a lookup at ARIN:
As you can see, the authoritative nameservers for this IP is:
If you were getting your IP from this company (for example) you could not just enter a PTR record and have your problem solved. You'd have to contact this company and have them add whatever PTR DNS entry you want into their zone file for this IP range.
Now, if you tell me that your DNS is actually authoritative for your IP, then I guess we go to Plan B... but seems unlikely for a small web host.
Actually, as I re-read your question... you are not the web host, but an end user. You need to contact your web host about this. I doubt you'd have the ability to set your PTR record. Are you even sure it's your own IP, and not shared with other web hosting customers?