Yes you'll certainly be able to receive calls and texts on the sim
Is your account appearing active online with mobile number showing?Http://j.mp/my_giff
You can perform a sim swap on your account once the sim as arrived , but it's sent second class.
If you report it lost, it's send first class and you'll receive it 2 or 3 days earlier
To report it lostHttp://giffgaff.com/support/lost
And click bar sim only
( sim swap)
Click here and log inHttp://j.mp/swapsim
Put the 6 digit code in from your new sim
And click continue
On the next page it'll show the 6 didgit activation codes and sim serial numbers of your current and new sim cards
Click where it says...
"Yes I want to replace my SIM"
( on mobile browsers don't forget to scroll down to see)
On the next page click "yes I'm sure"
Your new sim will hopefully be active within 30 minutes
And your old sim will be disabled
( if the new sim dosnt appear active after 30 minutes try turning the phone off and on)