Yes, Samsung Galaxy A7 2018 supports 4G VoLTE. VoLTE or Voice over Long-Term-Evolution is the latest technology in India for high-speed internet and communication. It works on band 3, 5 and 40. Since the Samsung Galaxy A7 2018 supports Band 3 and 40 in both the sims, so it supports VoLTE along with 4G in both sims.
You can find the complete set of specifications of Samsung Galaxy A7 2018 here: Samsung Galaxy A7 2018
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It is difficult to choose between Samsung Galaxy A7 2018 and Oppo F9 Pro. If you are a photography lover and plan to utilize your mobile for taking high quality pics, you must go for the Samsung Galaxy A7 2018. Otherwise, Oppo F9 Pro offers you a better configuration in terms of RAM, front camera and battery backup. So it is now completely up to you what your motive is to use a phone.
You can check the comparison here: Samsung Galaxy A7 2018 vs Oppo F9 Pro
It's a tough battle between these devices, as on one side Samsung Galaxy A7 2018 has a better processor and it also has a better camera while on the other side Samsung Galaxy M30 has a bigger screen and very powerful battery backup.
To see the complete comparison between these devices: Samsung Galaxy M30 vs Samsung Galaxy A7 2018
Out of these, Samsung Galaxy S8 has much better display quality, better performance, has wide-angle selfie camera and it also has fast charging support.
To see the full comparison: Samsung Galaxy S8 vs Samsung Galaxy A7 2018
Prashant Raigur Pacific