China Telecom Shanghai has denied claims that it has slowed down connections to overseas websites to encourage customers to sign up to premium services.
Frustrations in trying to connect to overseas sites are simply down to large numbers of users and limited Internet resources, insisted the telecoms giant.
A China Telecom Shanghai official said that work is currently taking place to upgrade its international connections.
This follows complaints from customers at the delays trying to connect to sites such as Amazon and Apple's App Store.
In a test by Shanghai Television, it took more than 10 minutes for a China Telecom account holder to open the home page of the Microsoft website.
An account holder with rival China Mobile network on the same computer took only a few seconds to open the page.
And an Internet speed test by the TV station found the speed of the China Telecom Shanghai connection was as low as 1 kilobit per second.
Access to foreign websites was almost impossible during the evening, the peak time for Internet use, said the report.
But some users claim this is a marketing ploy to get customers fed-up with waiting to sign up to a more expensive package.
China Telecom was until recently offering its International Elite Network package, charging users up to 200 yuan ($32) a month to provide faster Internet access to overseas websites.
While new sales for International Elite Network have been stopped, another package, the oddly-named Nitrogen Cylinder, is now being promoted.
Under this scheme web users are offered faster access to overseas sites for 2 yuan per three hours.
Shanghai Television recorded a China Telecom service hotline operator warning a customer that their connection could be "very very slow it you don't buy the new package."
One disgruntled web user on online forum v2ex.com photoshopped the company's "connecting the world" slogan to read "connecting the world … for a little extra."
But China Telecom Shanghai insisted the problem is solely due to the pressure of numbers on its servers and that it is working to solve this.
"We are upgrading the capacity of our international network servers, and the work will be done by the middle of September," said Xu Zhenyu, general manager of China Telecom Shanghai Internet operations department.
"Until then, users will have to put up with some congestion when visiting overseas sites," he added.
"Our service fee will remain the same after the upgrade."
In 2014, China Telecom Shanghai had 70 percent of the city's market for Internet service providers.