If you're expecting to travel outside the EU (or maybe even inside the EU if things don't go well) it's really necessary to plan ahead because of the high call charges. GG is cheaper than most other British providers, but even so at a quid a minute to send and receive calls using a mobile outside the EU is a very expensive business. Think before you answer your mobile outside the EU - you'll be paying a pound for each minute!
Some things to do before you go:
1. Spend some time researching (on the net) about free wifi at your destination. With wifi it's possible to access the net and use free messenger apps for calls and texts.
2. Download free messenger apps and encourage people that you call often to install them too. I use WhatsApp and Line for most of my calling now.
3. Research availability of cheap data/call sims at your destination, and where to buy them. If you have an old phone that supports wifi hotspot think about using that with a cheap data sim to provide mobile wifi for your main phone. That means you will not have to remove your UK sim from your main phone and it will still work for calls on your UK number and will still send/receive texts.
4. Tell your family and friends to use texts if they need to contact you urgently and can't get you via a messenger app. Texts cost nothing to receive, but please keep in mind that they do cost 30p a go to send.
5. Research calling cards at your destination. These prepaid card will let you call the UK or elsewhere at cheap rates from landlines, and often will work from hotel phones and public phones. Check with your hotel first, because some make a big charge for an outside line.
6. Research local English speaking emergency numbers and add them to your phone's contacts. Apart from the usual ones, it's a good idea to have the British Embassy's emergency number, a local English speaking doctor/hospital. Also the international number for your airline, travel insurance, credit and bank card providers and so on.
7. Don't forget the bits and bobs. Almost all chargers are now multi voltage, but it's worth a check. Dont forget to take an extra USB charging cable if your charger has an integral cable so that you can use USB power ports. And definitely check the electric plug type at your destination and take a converter if necessary.