Very straightforward. No question asked. Just call 1111 and tell them you want to request for public ip.

They will insist to send technician home. But you can just diy and let the tech know its all good when he make visit call. And send him some requested screenshot and pics maybe.

Try check speed on cable first to narrow down the issue.

Also when people complain about wifi getting slow after a while, lots of time it has to do with channel congestion.
do wifi survey and make sure there are no other radio contesting the same channel.
auto channels sometimes is not very reliable and will insist on broadcasting on that one congested channel when there are lot more better options available.