Competition between mobile phone networks in the UK means it’s good to own your own phone, and take out one-month SIM-only contracts to keep yourself connected for voice and data.

These days, moving between networks is a doddle, thanks to the ability to change your provider with little notice, and keep your precious phone number. Or so I once thought.

Don’t get me wrong, I’m not an inveterant switcher who never stays on the same network for more than six months. I had to switch to O2 after 13 years with Orange in order to get an iPhone 3G.

When that 18-month contract expired, I did hot-foot it to Vodafone after experiencing first-hand the pitfalls of O2’s over-stretched network. That was almost two years ago, and I remained pretty happy with Vodafone ever since.

But in my experience as a reviewer of mobile phones, dongles and 3G-connected tablets, I’ve found the Three (3) network to have consistently faster 3G performance in the – admittedly limited – parts of the UK I travel. Couple that with the very attractive pricing offered by Three, especially for SIM-only deals, and I’ve found myself recommending Three to family and friends looking for good performance and very competitive prices.

So with an unlocked phone and the chance to save five quid a month and yet get a bigger data allowance, I decided to put my own money where my mouth was. And called up Vodafone for a PAC code, followed by a call to Three to start a new SIM 300 deal.

Not so painless transition

That was 12 days ago. And today, four SIM cards and a dozen phone calls later, I now find myself with no telephone connection at all. Still waiting for Three to get me back on the circuit.

Here’s what happened. First call to Three sales established that, yes, I definitely wanted the SIM 300 plan as that was only one of two advertised for the Apple iPhone 4 or iPhone 4S, requiring a Micro-SIM card.

The envelope from Three arrives two days later in the post, containing not one but two full-size SIM cards.

When I phone Three customer service, this time transferred to India rather than Glasgow, I’m told a replacement Micro-SIM card would be sent out. And it would take up to five days.

I bite my tongue and patiently wait five days. When no Micro-SIM arrived after five expectant days, I call again. This time I’m told, sorry about that, should have arrived, but you’d be better off going to a Three shop and collecting one in person.

But never mind, I’m told, because a Three shop can activate the card instantly, rather than keep you waiting 24 hours. The £5.11 cost for a replacement card was generously waived; and £5 credit, I’m told, credited to my account for the inconvenience.

On Monday, I collect a new Micro-SIM from Three’s shop in the Brunswick Centre, London, close to PC Advisor’s offices. The process is relatively pain-free, except I’m now told they cannot activate the Three Micro-SIM in the Three shop; I’ll have to phone up Three customer service again to get my new account working.

So I call Three on return to the office, where I’m predictably told I must now wait ‘up to 24 hours’ to get service. I give my PAC code from Vodafone, as required, in order to port my long-cherished mobile phone number across.

The following morning, 24 hours later and still with no Three service, I call again. Where I’m told ‘the process to activate the Micro-SIM is a little different, I must do it again’. And I, as a hapless customer, am asked to wait another 24 hours.

Still, I ponder, at least my old Vodafone number is working and I can keep myself connected to the world. But only, it turned out, for another two hours.

With No Service now shown by either Vodafone or Three, there’s just a promise that my Three Micro-SIM will now be activated after another ‘up to 24 hours’.

At various time, I’ve been told to try switching my phone off and back on again. Or removing and re-inserting the SIM to see if that works.

Surprise ending

Then I found myself this morning wondering if I should try that with the first replacement Micro-SIM card that finally arrived Tuesday morning in the postbox, over a week after it was said to be sent.

Magically, this works. And I’m finally connected as of Wednesday 16th November, 12 days later.

Three’s seemingly poorly trained staff aside, the performance was as good as I remembered – better in fact. From my home I benchmarked 4.91Mbps download and 1.59Mps up.

From our offices in the Euston Road? A staggering 6.35Mbps and 1.34Mbps. With a useful 1GB per month allowance and 300 minutes, it'll still be a great deal – once the bad taste of Three’s activation and sign-up process goes away.

If there is any lesson I learned, it’s that the overnight process of porting your number to a new mobile phone contract may not necessarily be overnight.