Would be interested to know the outcome of this. especially as using a personal phone can open up the issues of work calls/whatsapps when you are not being paid for work. Also if you are expected to use your phone whilst working as a driver then there should also be suitable training and risk assessment for you to undertake to ensure you are acting safely and legally whilst employed.
If you are on min wage and you have to use your phone then you are now being paid UNDER minimum wage, that is a story in itself.
If the phone is to be used for work purposes eg. to call if you are going to be late then it should be provided by the employer. Unless of course it is in your contract T&C that you must use your phone for "XYZ" then you have agreed to it. (this does not trump min wage though)
If they can just "replace you with a weeks notice" are you classed as a contractor as opposed to an employee?
A union, (I know this) will thump their fist and say that you must be paid however if the company you are working for is just scraping by and keeping you and your colleagues paid then it would be a bit of an own goal to cause them more cost.
If you are comfortable with it and don't think that you will become a target, have a discreet chat at first, especially if you have a good relationship with them, amicable situations may be closer than you think. a good start is " a couple of the guys have been mentioning...."