If you compare this bill to last month's bill you can see what changed. If you did not go off special pricing period (not the contract period length), the cost moves to regular price.
Taxes, fees, can change any time.
This is the same for any utility company. You stop paying and you may lose service and will owe late fees.
When you first sign on you are ussually getting special lower price offer. That price is never renewable. If you continue on it goes to regular pricing which most of us have paid for decades.
If you call the Comcast number, or go to a service center, to upgrade, downgrade, or get additional services offered, you may get some discount on regular price for a new period. That goes to regular pricing after any new offers expire.