Product differentiation for various markets and price discrimination are both common techniques that even a monopoly can use to extract more profit.
They know that not everyone would be able to afford the top tier of service. If Toyota were the only car company, they wouldn't only offer top end Lexus models. They would probably retain the various tiers, and simply try to capture the maximum consumer surplus at each tier.
There's no particular reason why a monopolist would want to remove a cheaper priced but lower functionality service, so long as it is profitable.
By integrating the businesses they might actually be able to find efficiencies and cost savings that make it even more profitable via economies of scale.
Whether those efficiencies end up as consumer savings is a question of how competitive the market is, but I don't see how this would necessarily harm the customer experience.
Might be able to reduce redundant storefronts, headcount, software as a service platforms, etc. Might be able to save money on employee benefits by leveraging larger group policies. They could do all of this while keeping things about the same or better for customers.
The only reason to actually eliminate the lower end of the pricing model is if it is unprofitable. Others would fill the space if they just killed it.