UK players have moved from using phone bill deposits, which often had limits...

https://post-wiki.win/index.php/Why_Did_Phone_Bill_Deposits_Get_Extra_Scrutiny_After_the_Credit_Card_Ban%3F

UK players have moved from using phone bill deposits, which often had limits like £30 per transaction, to faster, more convenient options. Modern methods like Faster Payments allow deposits as low as £10, clearing almost instantly