"other Dos Attacks"

I recently have been having large slow downs in my internet speed.  I was told by an AT&T tier 2 tech that the reason is that the logs show that there are numerous "other dos attacks" hitting my IP address and thus my internet speeds are slow.  I asked him how we could fix this and he said he did not have a solution.  He said that the best bet would be to change my IP address but he didn't have the tools available to do that.  He asked me to call customer loyalty to have them help me.  Customer loyalty in turn told me it should be technical support who should help me and I've been sent in circles with no one knowing how to fix this problem.  If someone can help me that would be great.   I've already had my modem reset to factory settings and also had a new modem sent to me but neither fixed the problem because the IP address stayed the same.  If anyone has any suggestions I'm all ears!  When AT&T tech support tells me they don't know what to do I don't know how they expect me to fix it :(

Thank you!