Whether it’s watching cats on YouTube, checking email or updating Facebook, if you go online while you’re out and about on your mobile or tablet, you’ll be using data.

Whether you are on a pay monthly or SIM-only offering, every month you’ll have a data allowance.

BT Mobile plans have 500MB, 2GB, 6GB or 15GB or data, BT Mobile Family SIMs have data allowances of 2GB, 6GB or 15GB.

Some things use more data than others, for instance downloading a song uses around 4MB or data, while downloading a 45-minute TV show uses around 600MB.

Use data to streaming video on Netflix or downloading a TV programme and you could quickly reach your limit and get a big surprise at bill time.

A 10-year old girl from London ran up a bill of over £1,700 watching loom band videos on her smartphone, while a mother from Edinburgh received a £718.69 bill after her eight-year-old son used her tablet to play Minecraft.

BT Mobile has some features to help you and your family avoid similar unexpected bills.

Set a spend cap

BT Mobile lets you set a spend cap on your bill for anything outside your included allowance. This means that even if you go over your allowance, you’ll know exactly how much you are spending.

To set a spend cap, log into bt.com/mymobile. Scroll down to ‘Tools to manage your spend’ and chose an amount using the drop-down arrow next to Monthly spend cap, choose a spend cap from £5.

Family SIM

According to Ofcom* just 54% of parents of children aged 12-15 and 40% of those of children aged 8-11 put a limit on the amount of money children can spend.

With Family SIM, however, parents don’t have to worry about their children (or other family members) running up high bills. You can set a spend cap for each Family SIM.  

Family with phones

What’s more, different family members can have different spend caps, for instance with young children who might not really understand how much things cost, you may want them to have a lower cap.

Family SIM spend can be set at bt.com/mymobile.

Text message alert

BT Mobile will send you a text message when you are close to your spend cap and another once you reach it. With BT Family SIM the SIM user gets a text when they are near their limit and when the cap is reached, the user and account holder both get a text.

If you find you are using more data than you expected, you can adjust your use.

Keep an eye on your spend by logging into bt.com/mymobile to check how much data you and any Family SIMs have used.

Going abroad

Go abroad and you leave your home network – this is called roaming. Roaming charges are typically higher for calls, texts and in particular data.

BT Mobile can help you avoid unexpected bills by setting a Data roaming cap, this can be done at My Mobile. Under Tools to manage your spend look for When you’re abroad.

With Family SIM you can set a data roaming cap for each individual SIM, so you won’t get a surprise at bill time.

Read more in our article: Going abroad with BT Mobile: How to save money with add-ons and free wi-fi.

Use free wi-fi

BT Mobile customers can access the internet at five million BT Wi-Fi hotspots around the UK via the BT Wi-Fi app.

If you’ve got a Family SIM plan, each person can use the BT Wi-Fi app to get online away from home, so they can connect to the internet, check email or update Facebook, without using their data allowance.

Finance expert Jasmine Birtles has put together her top tips on how your family can save money by bulk buying.

BT Family SIM is available for BT Broadband and non-BT Broadband customers, find out more at www.bt.com/familySIM. Use the Family SIM calculator to work out how much you'll save.

*Children and parents media use and attitudes report 2015