Short answer: it is the same 5.5% service charge if you do it online.
Unlike FSM who started its business as an online platform, PM is among the oldest UT company and it grew larger with the aid of its large independent salesforce - the UTCs or sales agents.
I think it will be hard for the company to undercut its UTCs without some sort of agreement and compensation. Similar to putting in robotics and machineries into a factory to replace manual labour and simply sacking the workers without retrenching them with retrenchment benefits.
Before you can register to the online PMO service, you must be a client first - meaning you must sign up with an UTC, who will go through with you a set of forms - which is basically to get your acknowlegement that you fully understood what you are about to invest into ie. can't complain later that the company or its UTC 'cheats' you if you lose money.
Within PMO, the service charge will be the same 5.5%. There is also an option to link a new purchase to the UTC, and you can also select 'no agent', whereby (if I am not mistaken) the service charge will then go directly to the company.
Select "No Agent" if you wanted to convey the message that selling mutual funds is a sunset industry, and to hasten its natural death. Hopefully, you would then get some discounts on the service charge before you grew old and retired.