Plan upgrade not logical

Hi,
Plan upgrade not logical

I will try to explain my concern.. But I explain my plans before:
Plan A is free for 6 months: renewable to B or C
Plans B and C are paying and crescendo rate. The B is more expensive than the C. These 3 plans are in the same category.

Doesn't make sense to me...
The TOTO member took plan A, OK, it's rolling. A few days later TOTO takes plan B, Ok it's going well
Plan A has become inactive and plan B is therefore active, it's still rolling
When TOTO returns to plan A, he finds that he can go from plan A to plan B!?!
So here I don't understand why there is this subjection since TOTO's plan A is indeed inactive in the bakend and in its profile.
Edit: TOTO has an active plan B, he shouldn't see this upgrade since plan A is inactive.
I hope you all understood.
Tell me where I could have made a configuration error
Thank you very much for your advice