Please check the above link for any network outages or work being done in your area.
@Lisatb Has there been any new high rise buildings been built in recent times between your home and the tower? That could cause a signal issue.
Hi there Lisatb,
What suburb/postcode are you located in? You may be an impacted customer due to recent severe storms/high winds/heavy rains.
Okay yep that can't be it then.
Next suggested steps would be to try your SIM in another phone and if the same issue, pop into an Optus store to arrange for a SIM replacement.