Infrastructure Upgrade??
18 billion invested, where exactly?? Be nice if they had a working infrastructure to start with, especially in the South West of England!
<rant alert>
We've had over a year of continual excuses and being ignored by Vodafone, they have non-existant 4G service in the South West and their 3G service has been terrible, so much so that 3G was turned off on all phones due to constant call drops and calls from customers sounding like Daleks. Even then call drops were still happening, but at least you could have more than a 10 second conversation with someone before having to find a land line.
My last network support ticket lasted nearly 3 months before their engineers 'fixed' the issue, which still isn't fixed. The one before that took 2 months to be 'resolved', and wasn't.
And don't get me started on the web site and customer portal, if you want to see what a site would look like if you gave a few hundred monkeys access to keyboards and a vat of jelly, go try and use it.
</rant alert>
tl;dr
Been with them for over 10 years, will be moving carriers come the new year, bunch of amateurs. This will bring it's own issues though, as the only other viable option is EE.
The state of the mobile infrastructure in this country is pathetic and 'coverage' doesn't mean squat if you don't have a usable service.