Genghis
Had a similar problem myself, but with Orange. Thankfully, and afeter nearly giving up, I managed to resurrect the phone I paid mega bucks for a few years ago when digital were first introduced, for £25.00. This is obviously much cheaper than the alternative of buying a new package and being left with an ‘obsolete’ phone. The reason the phone companies do not publish this little known fact is because they want you to commit to the more expensive option, from the horses mouth, as it were, and even I was misinformed by quite a few reputable outlets (Dixons (?)) that I could not get my original phone reconnected.
Out of interest with Orange if you buy the £50.00 voucher then calls become cheaper compared to the lesser value vouchers, ie, 25p peak 5p cheap versus 35p peak and 15p cheap (I think).