I don't understand your question: the literal answer is that you can "keep" your "bill" by not shredding it or throwing it away in the trash.
I suspect you really mean to ask whether you can assume your cellphone contract so as to continue with the same provider. In general, providers will probably terminate contracts unless debtors pay all arrears on their cellphone bill in full, which implies that they need to separately classify the debt in their plan. Whether that would be allowed depends in major part on whether they can get a cellphone account with another provider -- given number portability, there may not be a compelling reason to stay with the same provider. If they do not have substantial arrears, however, they can often simply indicate their intention to assume the contract in their plan.
Since chapter 13 practice differs substantially from district to district, and even from judge to judge within the same district, you need to ask your own attorney for advice that applies to your particular situation.
Bankruptcy laws require you to list all existing debts. There are no exceptions, so don't put yourself in the position where you are breaking the law. As long as you continue to pay your cell phone bill, you will be able to keep your phone. Hope this perspective helps!
Practically speaking, utility bills that you pay every month do not need to be listed in your bankruptcy ... unless you wish to switch companies and reject the contract you have with your current provider. Just keep up the payments to your phone company, your gas & electric company, your trash service, your water bill, etc ... and you will continue to receive service.