Mobile networks in Andaman are of huge concerns for travelers visiting the Islands. Basically, nothing works properly and the ones that work works at a basic level. And Yes, forget about anything called 3G or 4G in the islands. Surfing youtube is still a dream for many in the islands. We are at least 5 years behind when it comes to the network connectivity and internet in the islands in comparison to mainland India. Any attachment that you forgot to download will be a difficult task to download here in the islands. When it comes to mobile networks be careful as what carrier sim card you are carrying in the Andaman. Reliance Jio and Tata Docomo doesn’t work in Andaman. You will need to change your preferred carrier in case you are carrying sim cards from these networks.
So the mobile networks are mainly Airtel, Vodafone and BSNL. Among these nowadays it looks like Vodafone is providing the most clear signal. In Airtel, there is a lot call drop and in BSNL a lot of disturbance in the line. See in case of decent weather all works the same, but in a case of bad weather, I think Vodafone comes handy. I have had a personal experience with Vodafone and even until June 2017, I believe Vodafone stands out among other networks. I will rank BSNL as the second option and Airtel at the last for now. Though if you are carrying any of these networks to Andaman then you will be connected at least.
The second thing to know is while traveling to other islands BSNL might come as a savior as at some parts of the islands BSNL works better and in some Airtel or Vodafone. Around Radhanagar beach (Best Beach in India), Elephant beach at Havelock, Jolly Bouy at Port Blair no signal can be seen in your mobile irrespective of whichever operator you use.
Considering the remote locality of Andaman such things comes as a part and parcel of a tourist destination. Make sure your tour operator is aware as to where you will be visiting during the day so that in case of bad network connectivity they can send a person for any assistance. At Experience Andamans, our representatives are at most of the places where such network connectivity issues are present and they coordinate/help any traveler who is in need of assistance.In addition, sometimes we provide an extra sim card to travelers who are facing issues with their network operator after arriving in the islands.