T-Mobile are happy to allow customers on their Web'n'Walk Max tariff to use VoIP on their handsets (such usage is advertised as part of the tariff package). With unlimited data (10gig a month 'fair usage') data usage is not really an issue. This is why I changed from Orange (after 9 years) to T-Mobile 6 months ago. Just fyi, the relevant T-Mobile tariff costs £55pcm.
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T-Mobile are happy to allow customers on their Web'n'Walk Max tariff to use VoIP on their handsets (such usage is advertised as part of the tariff package). With unlimited data (10gig a month 'fair usage') data usage is not really an issue. This is why I changed from Orange (after 9 years) to T-Mobile 6 months ago. Just fyi, the relevant T-Mobile tariff costs £55pcm.