The rice has probably done all it can
What makes you say that? If the rice is absorbing water, then it’ll continue to do so.
What you need is a humidity gradient – inside the phone is humid of course, and you need it to be not humid outside the phone so that the water evaporates and exits the phone. This is what the rice is meant to be for.
However I’m unsure rice is going to be all that effective – after all, you don’t keep rice in sealed containers and it doesn’t continually absorb moisture. If I were you I’d go to B&Q and get some of the calcium chloride they sell in tubs for moisture traps. Put some of this in a box and seal the phone in there BUT you need to make absolutely dead sure it doesn’t come into contact with your phone. A dual compartment or some sort of shelf affair would work.