I have my home phone No. clearly marked on my van, and my mobile.
If they ring my home phone and no-one answers, the answer message gives them my mobile No.
It works good. Some don't like talking to answer phones so they ring my mobile.
But, sadly so far...No-one has phoned from my van writing. I think Van signs are mainly subliminal. They give you an identity, make you look like a legit business, but that is about it.
Mind you, once you' ve spent out on van signs, from then on free advertising, wherever you are. So, not a waste of money if you can afford it, better than the unmarked..."White van man".