I have a Samsung Galaxy pre paid mobile for work with a Tesco Sim Card.
Essex tours have always worked well for me and I've never had a problem until recently. I too had this problem of having my phone bombarded with calls when I was in Essex and after 2 days I gave up the tour. The Modus Operandi of the caller / callers was identical to the recent post about woman being bombarded with calls whilst touring Reading.
My callers started at 9am and stopped at 9pm (Daily

)
I've since googled "How to block with held numbers on a Samsung Galaxy" because at first it didn't appear possible. There's load of tutorial online and I've now managed to block the calls.