UPDATE 1-Italy watchdog probes mobile operator 3's prices

(Adds H3G reaction paragraphs 5-6)

ROME, July 19 (Reuters) - Italy's antitrust watchdog said on Saturday it was investigating complaints that Hutchison Whampoa's (0013.HK) H3G had charged excessively high prices for its mobile Internet services.

The AGCM agency said it had ordered the company, which trades under the name 3, to suspend some invoices for the service after unwary customers said they had received bills as high as 10,000 euros ($15,850).

It said it would now look to see if customers had been properly warned that if they exceeded a 5 gigabyte per month limit they would be charged at an "extremely high" rate.

The order to suspend invoices affects prices charged for services above that 5 gigabyte limit between September 21, 2007 and the end of May this year. After that date 3 altered its billing system to stop such high charges, the agency said.

H3G said in a statement that it had suspended seeking payment of the bills in question pending the outcome of the probe, saying a "few hundred" cases were involved.

"3 Italia reiterates the correctness of its operations, including the way the offer was structured which, with its 5 gigabayte per month ... is among the most competitive on the rapidly expanding mobile broadband market," it said. (Reporting by Robin Pomeroy)