The double blow of a maturing voice market and a sluggish local economy has not made life easy for South Africa’s telecommunications companies.

Vodacom’s revenue was up by only 2,1% to R77,3bn and earnings before interest, tax, depreciation and amortisation (Ebitda) fell by 1,5% to R26,9bn for the year-to-end March.

There is a similar story at MTN where its South African operations saw revenue fall by 3,9% to R38,9bn and Ebitda fall by 11,1% to R12,5bn for the year to December 2014.

Fixed-line operator Telkom was not spared. Operating revenue increased by only 1,2% to R31,7bn and its profit for the year to March fell by 19,5% to R2,9bn.

Though these companies have problems that are specific to the telecoms sector, they are also feeling the impact of an economy that has not fully recovered from the 2008 financial crisis and the uncertainty arising from Eskom’s ability to provide a constant supply of electricity.

“They are seeing the the impact of people trying to cut corners. If they can save R100 or R200/month by spending less on calls, they will do it,” says Irnest Kaplan, MD of Kaplan Equity Analysts.

The only upside is that all three have seen a significant rise in the demand for Internet access. Vodacom says for the quarter-to-end June, data revenue accelerated by 35,2% to R4,8bn and active data customers grew by 10,8% to 28m.

For its part, MTN South Africa’s data revenue for the quarter to end-March was up by 21,8% year-on-year and now contributes 27,7% to total revenue.

Telkom also saw significant growth in its data products with mobile data revenue rising by more than 50% to R988m and fixed data traffic volume rising by 32% to 33 petabytes.

Though the growing demand for data is a good news for the sector, it also means companies have to make significant changes to their business models. Under the old voice business models, the operators used to charge a premium rate for a service that did not require their customers to stay on the phone for long; average usage for prepaid users was only about 30 minutes a month.

The advantage of this model was that it meant their networks did not have to carry a lot traffic per user for them to make substantial profits. The days of this model are now on the wane as a saturated voice market and political pressure to bring down prices is taking its toll.

In becoming data providers, however, the mobile operators are in effect becoming utilities by adopting a strategy that sees them charging substantially lower rates and hoping their customers use their service as much as possible.

This shift requires them to make substantial investments in their network and to get access to fixed-line infrastructure to reduce the cost of providing the service.

This is what Vodacom is trying to do in its R7bn bid for Neotel, which has access to a national high-speed fibre network. It also spent R1,7bn on capital expenditure, mostly related to expanding it 3G and 4G/LTE sites.

Though MTN is also committed to expanding its 3G and 4G network, in many ways it has more options than Vodacom. Its Nigerian operation remains a significant driver of growth and the lifting of sanctions in Iran means it is free to repatriate about US$1bn (R12,9bn) it had trapped there.

If MTN gets its data model right in South Africa, it could use it as a template for its foreign operations when their voice markets start to mature.

But even if the telcos get their data models right, it will still take some time for data to become the dominant driver of earnings.

Kaplan says this is no reason to see the telecoms companies and the mobile operators in particular as troubled investments. “Don’t confuse not growing with them not being good investments.”

He argues that in an economy where most other large businesses are struggling, these are resilient companies which can still afford to pay out dividend yields of 5% to 6%. This is on par with a return an investor can get from a fixed deposit, and that excludes the possibility of capital growth.

Kaplan has a point. MTN’s dividend yield is 7,5% on a share price of R214 and Vodacom is 5,5% on a share price of R141,47. Even Telkom, which has not issued a dividend since 2011, declared an ordinary dividend of 215c/share and special dividend of 30c/share this year.

The businesses may face some challenges, but there is one other reason why they should not be dismissed as an investment. “What other large businesses collect their cash before they sell you the product?” he asks.