Customer support advised that Toggle Mobile provides unlimited free incoming calls in the US. A US phone number is free but expires after 30 days. To avoid expiration of the number, there's a £5 per year subscription fee.
The least expensive SIM card I see available is £25 and comes with a £20 credit. It seems this compares favorably against TruPhone, especially considering that Toggle charges 3 pence a minute outgoing versus TruPhone's 9 cents a minute outgoing.
Presumably you also avoid the issue of TruPhone's voicemail picking up too quickly if you go with Toggle.
I'm still uncertain whether Toggle uses T-Mobile in the US and thus can use 2g phones.
This sounds a little better than Truphone at 3 cents per minute vs 9 cents per minute for outgoing calls, even given that data is 16 cents vs Truphone's 9 cent per mbp.
What happens when the US# expires after 30 days? Is a new US number auto-assigned or what? I ask because I would be using the phone with GV and don't care what number I have as long as it's a US#. Also, Truphone using AT&T in US may be better than Toggle Mobile using T-MO, depending on one's needs. Thanks for post, for I wasn't aware of Toggle Mobile.
After 30 days the US number automatically drops. You could renew it every 30 days, but I would imagine you'd be assigned a new US number each time. If you subscribe to keep the same US number indefinitely, it'll take £5 out of your balance once a year.