If you have a smartphone, chances are you’ve downloaded at least a few apps. While many apps are often free, do they save us money? They frequently do, but there can be hidden costs.

When apps aren’t in use or lying dormant, they can still drain your data faster than you can say: “There’s an app for that.” The result can be a cell phone bill full of more nasty surprises than a Donald Trump video. Some cell providers will sting you badly on the slightest overage of your monthly usage; a stark reminder of how free apps can be expensive.

Here are 5 ways to save money and data:

1. Watch your back

Apps can gobble up precious data in the background, thus jacking up your monthly bill. To prevent this from happening, go into the data manager on your phone to see who the “greedy” apps are and then either set it to restrict background data, or turn them off completely. Some of the biggest data thieves are Facebook, Spotify, Instagram and Snapchat.

2. Know your limit, stay within it

While likely ineffectual words in preventing problem gambling, it can be invaluable advice for avoiding those unwanted data charges. Set reminder alerts (i.e. when 80% of monthly data has been consumed) to let you know when you are approaching your data limits. Free Apps such as My Data Manager (iOS and Android) and Opera Max will help you manage your data.

3. Compress your data

Browsers like Opera and Chrome have settings that enable you to compress data. For example in Chrome-> settings->bandwidth you can turn “reduce data usage” on, in addition to only allowing preloading of web pages when connected to Wi-Fi.

4. Take it offline to save data

Apps such as Google maps and Spotify allow you to use them offline. On Google maps, for example, you can pre-plan by mapping out the route you want to take then downloading it while connected to Wi-Fi. You can then use maps to navigate while travelling, without using any of your valuable data.

5. DIY

Apps and sites like Facebook may automatically play videos, which can quickly eat up your data. Go to settings -> videos -> auto-play videos and set it to “off.” You will then be able to manually play the videos when you’re connected to Wi-Fi.