Yes, you can deduct the total cost of your phone and internet for the year as communication expenses - if you used them exclusively for business purposes.
Otherwise you need to allocate the total cost between business and personal use.
You say you need to allocate the total cost between business and personal use.
Does this mean I can approximate a percentage of business vs personal use and then deduct that calculated business percentage on the expenses portion of the Schedule C line 25, or do I have to deduct it through the home office deduction line 30?
I would rather deduct Internet, cell phone bills, etc. on Schedule C, but if I am filing a home office deduction, do I have to put internet and cell phone deductions on line 30?
If you'd rather claim it directly on Schedule C, as opposed to Home Office Deduction form (8829), you can do it.
Make a reasonable estimate of how much time you spend on the phone/internet for business and how much for personal needs. I would recommend documenting your logic. Ideally, if you can request an itemized billing from your phone company for three month and go over it separating business and personal calls, that will give you a very good estimate. Either way, once you determine your business use, you can deduct it directly on the Schedule C: either line 25 or 27.
Deducting the expense on a home office deduction form allows you to avoid the reasonable estimate of usage. You just deduct it based on the square footage of the home office area.
See some more info in this article.