It seems T-mobile are trying to boost sales of their Flext tariff by offering FREE WEEKEND CALLS on Flext 35 & above tariffs.
This is a online promotion only
# Free weekend calls subject to connection to Flext 35, 40, 50 or 75 or Flext + Web'n'Walk 35, 40 and 50 on an 18 month minimum term contract. Also available to registered business customers on a 24 month minimum term contract.
# Subject to credit check.
# Only available via the T-Mobile online store.
# 5,000 minutes of free weekend calls a month. Your usual price plan allowances and charges will apply once you have used up your 5,000 free minutes a month.
# Free calls are between midnight on Friday and midnight on Sunday and are for calls from the UK to the customers of any UK mobile network and to local and national numbers.
# You may lose eligibility for the free calls if you move to another price plan.
# You will lose eligibility for the free calls if you upgrade or otherwise renew your minimum term contract.