I am very reluctant to use them - only if no other option. Glass sided ones facing out into a shopping centre are OK, as it is likely there will be phone signal and/or the ability to attract attention. However enclosed lifts are in my opinion a risk. In risk management, there are two dimensions. One is the likelihood of the event. The other is the severity of outcome. Trapped in a lift is low likelihood but high severity. Enclosed lifts are typically a metal box, which will act as an insulator against phone signal, therefore it is very unlikely a mobile phone will work. So, if the lift intercom fails, in the words of Captain Mainwaring, "We're doomed, we're doomed". I was going to ask if anyone has experience of the intercom failing, but alas, they probably wouldn't be here to tell us.
The severity is extremely low unless you are diabetic or require medication you don't have with you. It'd be no fun, but humans can do without water for 3 days, and thus one could be trapped in a lift for 3 days without coming to great harm, it'd just be incredibly boring and rather smelly once toilet use became necessary. Unless you were mucking about in abandoned buildings the chance of a stuck lift not being noticed for 3 days is basically zero.
The high severity comes from no way of extricating yourself, and a reliance on others, who may not be readily contactable.
But that's not high severity. Unless you had diabetes, you would not die even if trapped for a number of days.
High severity, low likelihood is something like a fatal plane or train crash.
If you're claustrophobic, as it sounds like you might be, it'd be very unpleasant, but you'd still not die nor be seriously injured.
I have to say I disagree with that. I've never heard of someone dying simply of being trapped in a lift - to say being trapped in a lift has a high severety is a little over the top, unless the building it's in happens to be on fire...
That of course being the reason why you are told not to use the lifts in a building on fire.