The problem with jmp.chat and Google Voice and all of their kin (all of those "disposable number" or "second line" apps on the various app stores) is the numbers provided by them are SMS-capable VoIP numbers and a significant minority of businesses will flatly refuse to allow users to use that type of numbers.
T-Mobile's DIGITS service was fantastic for this, at least for doing SMS with a number not attached to the SIM you have inserted in your phone, but they blocked almost all short-code senders when the service entered production.
What I do these days is give banks and businesses a mobile number attached to the second SIM in my iPhone. That number is on a prepaid carrier under a completely different name and address than mine. There's the non-zero chance that someday I'll have to "prove" who I am to that prepaid carrier and won't be able to prove that name. The odds of that are a lot lower than the odds of having my main number snatched from my mobile carrier just by an attacker knowing the last four digits of my SSN and persuading a customer service rep to swap SIMs on the "strength" of knowing this information.
I recently found jmp.chat [0] which provides an easy workaround for this.
[0] https://jmp.chat