Iphone data running out at home?

I'm looking to change my contract/sim to another network such as 02 as I'm currently on orange
Over the last few months I have been running out of data and going over my contract.
I assumed if you are connected to your internet rooter at home then your data isn't charged unless you are outside using Wi-Fi?
I'm nearly always at home and use my phone at home to go online and things but Sometimes it says 'no service' alot and I had to ring and get them to sort it out (it took over 45 minutes on the phone!)
and it went back to normal for around 1 week then did the exact same.
I was wondering if thats the reason its been taking my data
I use alot of social apps and games such as facebook, tumblr, instagram, twitter, and games.

Is Oranges rubbish connection the reason for my data loss?

When you're at home with Wi-Fi on, your iPhone should prioritise taking data through that network (ie your home internet) which SHOULD mean you won't be using any of your Orange allowance. If you're at home a lot and you've been charged it means your phone has been using your Orange data allowance over your wi-fi connection.

What you can do is go to your settings -> mobile data -> turn off mobile data. Your phone will then only connect via wi-fi when it can. This is great if you want to make sure you won't get overcharged for extensive data use.

If I was you, to be safe, I'd go for a deal (sim only for example) with a nice data allowance such as at least 1GB. All these modern apps download data far more than we realise as they are more modern and run like computers. It means you'll go through your allowance quicker. A plan with unlimited data is the ideal option. SIM only offers for this are surprisingly good value compared to conventional contracts. Try www.compare-sim-only-deals.co.uk to have a look or a similar site.

I hope this helps. I've been through the same thing. Networks charge a lot once your over their limit. It's how they make the majority of their revenue.