Good Morning,
Have you previously used the 02 Network at home, and if so has the signal been Ok in the past ?
Have you just changed to your current phone ?
Do other people like neighbours or visitors who are on the 02 Network have the same issue?
When you say "signal" is this 02 Network strength or 3G data coverage ?
Typically removing your sim and cleaning it removes static build up.
Another is to pick up a blank sim from any 02 shop and perform a sim swap whilst in the store or do it at home via this link.
http://swapmysim.o2.co.uk/
It can take from approx 2 hours to 24 hours for your services to fully return and by turning your phone off and on throughout this period helps to reset the services.
You can challenge the mast status by calling 02 Customer Services.
Contract Customers : 202
Payg Customers : 4445.
Also removing your sim card and trying it in another phone to see what signal you achieve will tell you whether the 02 Network has fringe coverage where you reside, or the signal returns then the current handset may have a fault.
Check the settings within the phone such as the APN settings and ask 02 to check your account too.
APN settings Link.
http://www.geeksquad.co.uk/articles/chapter/595-04-how-to-set-apn-settings-for-the-02-mobile-network
If its 3G your not receiving then change the settings in your phone to 2G to see if that improves, but you will have to put up with slower speeds.
02 do offer a service called TuGo which may be of interest to you when at home.
http://www.o2.co.uk/tugo/want-it
If you feel the handset may be at fault after checking out 02's side then seek assistance from Samsung.
http://www.samsung.com/uk/support/location/supportServiceLocation.do?page=SERVICE.LOCATION
If its 02 and a fringe coverage issue then another option is to jump Networks if the issue is such a concern to you whilst you are at home. Obviously ensure any alternative Network gives you better coverage by testing out a Payg sim from other Networks.
If you currently have an 02 Network locked phone then you can get it unlocked for free if your on Contract, or £15 for Payg as long as its been latched onto the 02 Network for 12 months.
Unlock Form.
https://www.o2.co.uk/apps/help/help?qid=1&q1=2&route=unlocking&case=Handset%20Unlocking%20Form
If on Payg just ask for your PAC Code and give this to your newly chosen Network.
If your on a Contract then you would need to pay off the remaining months of your contract minus any bolt ons. Some people have in the past sold the handset to help reduce the initial cost. Ask for your PAC Code, and give that to your chosen Network.
When the new network use the PAC this will effectively end your 02 Contract and they would send you the final bill.
I hope things resolve for you one way or another.
