DNS ISSUE! AHHH Cannot access my server on one certain isp

[smartman192]

So, after a few complaints from customers. I looked into it and found out that on certain a certain network my servers are not accessable. I cannot ping them, or anything.

The network in question is CenturyLink and possibly Sprint. (One in the same I know but seems to work on sprint)

My servers are on Comcast's network, never had any issue with them. I checked all my ip's and all are in good standing with everything. So nothing is blocked.

So can anyone in the world shed some light on how to resolve this? It's not like CenturyLink is the greatest at customer service.