[rubypudding]

I apologise if this has been asked recently. I have spent an hour or so searching this forum but I couldn't find an obvious answer.

I bought a payg K750i on the Tesco network a few months back and I'm thrilled with it. The only (huge) problem is the fact that I can't get a signal within a 1-2 radius of my house. I can't say this is a surprise as I my Orange payg was the same so I knew what to expect. However.........today I found out all the neighbours use Vodaphone and it works perfectly!!! So, here's what I'd like to know:

1) providing I can get it unlocked can I still use the Tesco sim but alternate it with the Vodaphone (I have about £20 of credit on the Tesco phone which I don't want to waste)

2) I know that I can change the sim/network and keep the same phone number but I'd rather do this when I've used up all the credit on the Tesco phone unless there's any way of having the same number on 2 different sim cards/networks of course.......?

Many thanks in advance.