return to previous subscription price after trying a different in-app level

I currently offer two in-app monthly subscription levels - "A & B". Current prices are A = $2.99 & B = $6.99 per month.


These same levels used to be priced lower (A = $0.99 & B = $4.99) and I have a number of users who subscribed at those prices and take advantage of the grandfathering option.


If a level A subscriber who is grandfathered at $0.99 decides to do a trial of level B (I know this will be at $6.99 as it's a change in level) but then switches back to level A, will they still get the grandfathered renewal for level A of $0.99 or would their trial of another level remove their grandfathered pricing?


Thanks in advance to anyone who can help with this!