The Hidalgo County auditor is looking into long distance calls made from the District Attorney TMs Office and the counties TM health department.
The bills have exceeded $400,000, but District Attorney Rene Guerra assures residents the county won TMt be footing the bill.
Action 4 News obtained documents showing how extensive the phone hacking is.
According to phone bills, someone was able to tap into both departments phone lines and make hundreds of long distance calls.
"The very first time that that phone billed showed, somebody in it should have jumped on it and investigated the phone bill," Guerra said.
The hacker called places like Taiwan, Canada and Gambia.
According to documents, the hacking started in March 2013.
A normal $50 to 60 bill jumped to nearly $3,000 for the health clinic.
In April, the bill for both the health and D.A. TMs office exceeded $200,000.
The hacking comes after a phone system change in the departments caused by employee growth.
"My office has grown from maybe 35 employees to well over a hundred, Guerra said. So every employee that is added on needs a telephone for communication."
On Friday, the D.A. TMs office received this letter from provider at and t acknowledging the counties dispute of fraudulent phone calls.
The company is investigating the calls, but now the cost is more than $400,000.
It TMs still unclear if fraudulent calls are being made, but the most recent bill in may shows the long distance bill is back to normal pricing.
"The issue is not resolved until we get a formal decision from AT&T," Guerra said.
The hacking did not compromise the department TMs security, according to Guerra.
Action 4 News spoke to the county auditor who is auditing the phone calls.
He said once his audit is done, Action 4 News can access that information.