A year after communities including Batemans Bay, Surfside, Moruya, Bega and Narooma all reported mobile and data services collapsing under the weight of increased usage by holidaymakers, carriers have completed upgrades to local service towers.

Telstra has spent nearly $2 million to add 4G coverage to existing 3G towers on the south coast, matching broadband internet and mobile data services available in metropolitan Sydney and Melbourne.

Local civic and business leaders campaigned for the upgrades throughout 2013, and some said on Friday coverage during the Christmas period showed signs of improvement for smartphone and internet users.

Moruya real estate agent and Chamber of Commerce member Lilian Brindley said last summer's meltdown could not be repeated as south-coast populations increased by as much as three times.

''It was dreadful before,'' she said. ''People would go to holiday houses and find there was no coverage, which is just essential these days for visitors and businesses.

''After a long drive, people would have to go all the way back to a spot where there was coverage. We got calls saying coverage wasn't working and that was very frustrating.''

Ms Brindley said peak demand on the south coast lasted from Christmas Day until the end of January, but she had heard from some visitors the situation had improved.

''People are absolutely concerned about coverage. In the real estate market, it is one of the questions people do ask when they contact us. Often, if people have looked at a rental property, prior to booking it, they come out and test internet coverage. It is a huge selling point.''

She said local traders and residents were optimistic the improved coverage would sustain the expected demand throughout New Year celebrations and January.

Batemans Bay Chamber of Commerce president Allan Rutherford said the next few days would be critical.

''Our business was affected firsthand by the problems last year so we will be keeping a close eye on how things go this summer,'' he said.

''The 4G technology Telstra has put in place already is a dedicated data network, so that is going to make a big difference once the peak period starts here on the coast.''

New antennas and upgrades have been completed at Ulladulla, Batemans Bay, Mossy Point, Moruya, Narooma, Merimbula, Bermagui, Tura Beach and Bega, welcomed by local government authorities and Eden-Monaro MP Peter Hendy.

Telstra said this month that it hoped customers would receive download speeds of between two and 50 megabits per second and that the network would not fail.

Coverage on the Kings Highway and in some regional communities remains patchy at best, prompting calls on social networking websites including Facebook for carriers to upgrade coverage areas.

Communities including Tathra, Eden, Wyndham and Merimbula have also called for relief from poor mobile and data coverage by carriers including Optus and Telstra.