Hiya i had the same problem you did and i tried phoning up 3 (my network) they couldnt do anything so looked online and found a software that will block call and text but for you seeing as your on vodafone try this
http://help.vodafone.co.uk/system/selfservice.controller?CMD=BROWSE_TOPIC&PARTITION_ID=1&CONFIGURATION=1000&SIDE_LINK_SUB_TOPIC_ID=1069&SIDE_LINK_TOPIC_ID=1007&TOPIC_ID=1069&TOPIC_TYPE=0&STARTING_ID=0&TOPIC_NAME=Dealing%20with%20nuisance%20calls&PARENT_TOPIC_ID=1007&PARENT_TOPIC_TYPE=0&SOURCE_FORM=BROWSE_TOPIC
or try this software download to your phone
http://tasikisme.net/block-unwanted-sms-on-nokia-with-mr-sms/
I dont know if you have a nokia but i tried the link and it successfully blocked calls and texts