Regarding Lightroom CC and Lightroom Mobile subscriptions

Generally the month to month price is cheaper than paying one month at a time. This is because, like a cell phone contract you make a twelve month commitment. So all Creative Cloud plans or the LRCC Plan have cancellation fees of 50% of the remaining contract. So for example if you cancelled after 6 months you would be liable to pay the cost of a further 3 months (50% of the remaining 6 months).

The mobile only version of LRCC for phone or tablet is a free app. So I believe a cancellation fee is not applicable. If you purchase premium services at $4.99 pm or local equivalent you can cancel at the App store, iTunes or Google play. AFAIK this takes effect at the end of your monthly billing period without any further liability. But check at the appropriate store or on your device Settings >> Subscriptions.