I ended up getting the problem solved by opening up a chat on MOA.
The customer care person confirmed there is no outage at the time, and said it was something wrong with my samsung and that it happens after 18 months. They said something else technical too but I don't quite get it. But here's the process they asked me to follow. What happened was it put 2 bars back on my phone and i was able to use 4G again. Later on that day, maybe a couple of hours later, i went back to full 4G bars.
Settings>Mobile Networks>Network Operator>Select Manually>Optus
Then turn your phone off for 45 seconds and turn it back on again
After I followed that, it brought 2 bars back and went back to normal a couple of hours later.
Brilliant, thanks very much for returning to Yes Crowd to let us know the outcome Mr_Windows! ☺️
P.S. What Samsung model do you have?