Well, you could always block their number (assuming they are calling your cell phone). I used to work for an attorney that dealt with debt collection. If the collectors can't reach you, we would end up mailing you a letter stating that you owe a debt to such and such company and basically if you don't pay up we are going to take you to court.
I was also on the receiving end of debt collection as well from mainland companies (I'm from Hawaii). If you really want to stall out the process in other words if you need a bit more time to pay (you can't really avoid paying), you can always respond back in a typed/written letter asking for proof of the debt and if they are licensed to collect debt in your particular state. For me it worked twice where the company sent one agency, I responded back for proof, didn't hear from them for an additional 2-3 months, got another agency doing the same thing for the same debt after, responded the same way. Then I realized okay, I might as well just face the facts and pay it off so it doesn't mess up my credit report any longer. Best decision ever.