EE says it has resolved "teething problems" with its new 4G network, which went live in 11 UK cities last week.
The super-fast mobile broadband provider has received a number of complaints from customers since services went live on October 30th.
Some have reported difficulties connecting to the new network, venting their frustration on micro-blogging website Twitter.
And others attempting to connect to the 4G network have had trouble obtaining the correct SIM card.
A spokesperson for EE admitted the firm has experienced some difficulties with the launch of 4G services in the UK.
"In a small number of instances in week one, a gap in a process on SIM distribution has delayed customers in accessing the EE network," he stated.
"We have now identified the teething problem in this process and a dedicated team has resolved all issues it created on a customer-by-customer basis."