The service is currently not available on the network.

Tap Settings > More networks / Mobile networks > Access Point Names > MTN NG > Option > New APN, then enter:
Name: MTN NG
APN: web.gprs.mtnnigeria.net
Username: web
Password: web

The most effective and simple way probably is to setting your gadget into flight mode, if you don't plan on answering the phone in a long period of time. Also, charge your phone before its battery running all the way down. Lithium-based batteries are designed to be charged early and often. There are still other things you could do to prolong battery life: avoid using unnecessary features (using moving or animated pictures for background is not suggested), turn off Bluetooth/WIFI/GPS and avoid leaving your phone in a hot car or direct sunlight.

To fix Android heating problem, you need to：
• Reduce your gaming obsessions.
• Disable functions when you don't need them.
• Dust off your smartphone.
• Simply turn off your phone when you are sleep or in a business meeting, so your phone friend could "take a break"

So, sorry for what happened. I've actually experienced such too but it was promptly resolved when I got in touch wiv them thru their twitter handle @MTN180. I assure you of a prompt resolution when you do..

Take the phone out of the water as soon as possible.

Note: If the phone is connected to a wall charger and is also submerged in water, do not attempt to remove it from the water until the major power circuit breaker is switched off.

Quickly dab the phone with dry towel, while at the same time removing the battery cover and battery.

To find out if the phone is truly water-damaged, check the corner near where the battery is — there should be a white square or circle, with or without red lines. If this is pink or red, your phone has been water-damaged.

Remove the SIM card. SIM cards survive water damage well, but getting it out immediately makes good sense. Pat it dry and set it aside to dry out until you reconnect your phone to your cell network again.
Remove the ear buds, memory cards, as well as any phone cases or protective covers. Remove all plugs that cover the gaps, slots and crevices in the phone to expose them to air-drying.
Gently wipe off as much water as possible without dropping the phone. Avoid shaking or moving the phone excessively so as to avoid moving water through it.
Use a vacuum cleaner to suck the liquid out of the inner parts of the phone. Hold the vacuum cleaner over the affected areas for up to 20 minutes, for each accessible area. Don’t hold the vacuum too close to the phone, as a vacuum can create static electricity, which is even worse for the phone than water.

Do not use hair dryer to dry out a phone as this may force moisture further inwards toward the crevices. You can however use a heater, fan or other air-flow device to blow air across the phone’s openings to aid drying.

Put your phone on a sunny spot to help it get rid of any water in very small places.
Test your phone. After you have waited at least 24 hours or longer if needed, check to see that every area of your cell phone is clean and looks dry. Check all the ports, compartments and in between crevices for any moisture or dirt. Wipe away any dust and dirt from the device and covers, and insert the battery into the phone. Attempt to power on the device, listening for odd noise and observing to see if the phone appears to function correctly.
Plug it into its charger without the battery if your phone is completely dried out, but still does not work. If this works, you will probably need a new battery.

For MTN international destinations bundle 1 of 50 minutes, text IDB500 to 131. Cost N500
For MTN international destinations bundle 2 of 120 minutes, text IDB1000 to 131. Cost N1200
For MTN international destinations bundle 2of 200 minutes text IDB1500 to 131. Cost N1500
Dial *559*1# to check balance. text 'STOPIDB' to stop Auto-renewal

Go to options
Select advance options
Select TCP/IP
Type the following;
In APN; web.gprs.mtnnigeria.net
Username: web
Password: web
Save
Doing thi,s you can use your browser without subscribing for BB.

Have you been feeling the Pulse?! MTN PULSE!

Get a free Gear VR powered by Oculus, plus a VR content experience – an estimated $150* value – with the purchase of a Samsung Galaxy S7, Galaxy S7 edge, Galaxy Note5.