I have 4 more days of Samsung refund warranty so today I have commenced my final effort to self-solve. My provider is a Telstra MVNO partner - AldiMobile. Similar to Woolworths, Telechoice and Better Life which do NOT have VOLTE (confirmed). So I bought a new Telstra SIM and asked Telstra to turn ON VOLTE on that SIM service (which is by default off). I am testing this today which will confirm if these dead spots have anything to do with mobile tower switching/VOLTE etc. Will test a couple of days and take second S9 back on Friday if this workaround does not work.
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