We live in an area where mobile phone coverage has many black spots. We have looked at smart phones that support dual active SIM cards with dual activation (DSDA) but have found little information on which phones available in Australia support this function. Does anyone know of phones currently available that provide this function and support the service in Australia? We have looked at the Huweii that has a dual sim function, but it seems to not provide the service here in Australia?
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Whistleout has an article about dual SIM phoned in Australia…
There are other models to that in this article as well. We have a Vivo Y17 that offers dual sims, but don’t use this function.
Most carriers only offer single SIM phones for obvious reasons…to to have dual sim functionality, one may need to have a BYO phone with a carrier (or two).
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Hi @VB49J, welcome to the community and thanks for your post.
You might find the following from Optus useful.
https://www.optus.com.au/for-you/support/answer?id=20007
This explains some of the requirements for dual sim phones.
There are two different modes of operation. Active or standby.
Optus lists two Huawei P30 models as suitable for dual mode operation.
Assuming your services are both 4G-VoLTE Optus advises you can have both services active concurrently.
Reading between the lines there are limitations in how 3G functions. Any incoming call that reverts to 3G will cause the phone to change into standby mode for the second sim. IE only one active connection.
Per Optus
When a phone is in Dual SIM Dual Standby mode, both SIM cards are active and can make and receive calls while they are both in standby mode (i.e. neither are in use).
Once one SIM card is in use (i.e. you take a phone call), the other SIM card becomes inactive for the duration that the first SIM card is in use.
This is because the two SIM cards in Dual Standby phones use the same receiver. Once a call on one SIM card is engaged, it will use the receiver exclusively and the other SIM will lose mobile connection.
To avoid missing a calls from one SIM while the other is engaged, you can set up call forwarding.
There are other more expensive dual sim Huawei phones that offer 4G or 5G if that suits your needs. Refer to Allphones or other online site perhaps for a sample. (https://www.allphones.com.au/mobile-phones/dualsim-mobile-phones) It would be best to confirm with a mobile phone supplier in writing whether the phone you are looking to purchase will suit your local network options. We have 4GLTE, but not 4G-VoLTE, so our voice calls are on 3G technology.
Our experience of poor to patchy mobile reception locally has been it is best to have two mobiles. One on each of the major networks. Our preference has been to find the mobile phone models with the best reception/range. Telstra blue tick or reliable reviews for guidance.
We did have a Huawei some time past. It was OK, but had over time other issues. When it is appropriate and we need to purchase a new phone the superseded one is used for the secondary service. The older phone goes to recycle.
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As already mentioned by others there are many dual SIM phones available in Australia, most of them being dual standby. Some can do 2 x 4G, some only 1 x 4G and 1 x 3G and a few can do ‘full service’ 4G for one, but only ‘4G data’ or ‘3G full service’ on the second.
My dated (2018) Moto has an Aldi (Telstra net) SIM and an amaysim (Optus net) SIM because depending where I am in my house one or the other works better, and sometimes only one or the other works, and sometimes neither has a usable signal although I am only 1km from the tower but shaded by a hill! 
As for dual active, consider why that is important. If you are on a call with SIM-1 and you get an incoming on SIM-2 do you really want to be interrupted to put the call on SIM-1 on hold, or would it be enough for the SIM-2 incoming going to voicemail as would be the case.
If one spends a long time per call and one is a business or has potential emergency calls it makes sense you would want dual active, but for the rest of us it sounds important until we consider how it works in a single phone, in practice. If your caller went to voicemail onSIM-2, or went to voicemail on SIM-1 since it was busy, do your callers know to try your second number if the first is busy and goes to voicemail? Of course setting call forwarding on busy would solve that, but. For both lines? It could be ‘exciting’.
Searching for DSA models results in confusing hits between DSA and DSS since it is a rare feature. It would be a service for all readers if ‘we’ can provide a list of local models that operate in DSA mode.
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