Should I take the memory foam from my shoes to put insoles in them? I have plantar fasciitis

i have a question,I buy oasics because I heard they are good for your feet if you have planters fisciatis,but I have insoles for my shoes that the dr made for my feet,in order to put these in my shoes I take out the thin strip of memory foam that comes in my shoes.My question is should I be doing this.My husband says no but if I put both in my shoes slip off cause my feet sit to high with both in.