Is PAYG mis-named and mis-sold?

I'm looking for a broadband plan for my mother, who currently uses dial-up. While checking all the options, I came to examining PAYG mobile BB and I'm shocked at what I THINK I'm seeing. If what I put below is incorrect, please let me know.

The first few websites that I've looked at (Three, O2 and Vodafone) all appear to me as if their PAYG is anything but PAYG, being merely a non-contracted Pay Monthly.

It seems that you get the dongle and buy a top-up. These come in very specific amounts rather than letting you choose how much you put on. Then, say you get a £15 top-up, this doesn't give you £15-worth of data - as a true PAYG would - but rather gives you 30 days to use whatever the stated download limit is. My reading is that once those 30 days are gone, any unused data allowance is lost and, unless you've bought another "top-up", you lose connectivity.

That's a con and mis-selling. It's not PAYG at all. It's a one-off single-month contract. Some companies appear to offer 1-day and 1-week packages. True PAYG would advertise a data rate and your credit would last until used up. If these exist, they are well-hidden on the sites.

If I'm barking up the wrong tree - at least with regard to the three companies named above - I'm happy to be corrected. Otherwise this is a huge scandal in my book.

[Admin]

If you can remember back to when Pay As You Go was a new part of the mobile phone market in the late 1990s, at that time all PAYG providers had the same kind of 30 day expiry on their top ups. As I recall, Orange was the first PAYG provider to remove the expiry on top ups meaning they became very popular and all the other providers changed their policies to match as they were losing customers.

In effect with the old model of PAYG you're buying a period of access to the service with a usage limit. It's kind of logical that PAYG mobile broadband should work this way as it's grown from the mobile phone PAYG data 'add ons' or 'bolt ons' that were around for some time before the first mobile broadband tariffs. These add ons gave you access to mobile Internet data for 1 day, 7 days or 30 days, each had an associated usage allowance which grew with the time period but they were primarily sold on time period.

T-Mobile's pay as you go mobile broadband is still sold as 'Pay By Day' and still has 1, 7 and 30 day options (interestingly, all with the same usage allowance).

There is currently only one provider offering Pay As You Go mobile broadband without top up expiry and that's Vodafone: Vodafone Mobile Broadband Top and Go Mobile Broadband

However they're only offering 1GB top ups, so depending on how much data you use, you might still find it better value to use time-limited higher usage allowance deals from other providers.