"After more than 20 years of close partnership, we have taken the hard decision to not renew our EE Mobile contract with Dixons Carphone, and shift our focus and investment to growth in our own stores and online channels," BT said in a statement.
"This has not been an easy decision to take and follows many months of challenging discussions and negotiation."
A spokesman for Dixons Carphone said its contract with EE to sell pre and post-pay plans would come to an end this month but current customers would be unaffected.
"We are well underway with our strategy of moving to a new, more flexible and transparent mobile offer that gives better value to our customers, and this offer is set to launch early next year," the spokesman said.
In April, Britain's O2 mobile network also cut ties with Dixons Carphone after it failed to agree a partnership deal.
(Reporting by Paul Sandle, editing by Louise Heavens)