Andriod service to I-phone service, is that really a thing? I thought Boost service!

I am on the $30 grand-fathered in Shrink and 5g Data plans that are no longer available with Boost. I have been using the Galaxy line of phones but now boost does not have or will get the phone I want, the Galaxy 8+. Switching to an I-Phone, which they have the 8+, they told me I would be paying more monthly and lose my 5g data package as it is all a different plan from Android to I-Phone!!?? Why is this so if it is with the same company? I do not want to pay more than the $30 I Shrunk to and I want to keep my 5g of Data plan!!! I just want the 8+ whether it is Galaxy or I-Phone. Anyone know the switching policies?

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