The advice to contact your ISP is only relevant if your IP address has become associated with spam. (Your IP address is a 'dotted quad', such as 78.123.832.27, that tells internet servers where you are). That's unlikely if you're using Vodafone PAYG, as your IP address almost certainly changes every time you connect.
It's more likely that your actual email address (e.g.
[email protected]) has become associated with spam. If so you need to contact your email provider (which can be identified from the bit after the @ sign in your address).