comCast or DSL (CenturyLink)

[pellaz]

I have a commercial internet account from ComCast, a local cable tv provider. Last week they did a service upgrade in the town and i lost a lot of my connectivity basically they cant seem to relate a name to its ip address. Having the commercial account my speed is guaranteed and i use the speed fairly consistently. ComCast tec support is like having a conversation with my Irish Setter.

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has anyone here had experience with DSL and CentryLink (formally Qwest)? This would also be a commercial account where the speed is guaranteed.
How is their tec support?