Call plan cost increase

[#1]

I was notified by email yesterday of my latest bill and it was slightly more than usual. When I checked it was because of a call made to a mobile. No problems there but what I did notice is that my all inclusive call plan is being increased from £4.50 to £5.00 monthly from the next bill onwards. Is it normal for costs to be increased without informing users?
Looks like I will have to analyse my bills to see if it is worth continuing with the plan as very few calls are made during the week and my unlimited fibre contract will give me free evening and weekend calls

[#2]

You were informed by ticket and associated email on or about the 6th August

[#3]

I'm not sure what you mean by ticket but neither of the email accounts linked to plusnet has an email referencing an increase in cost of the call plan.

[#4]

The ticket should be seen here https://www.plus.net/wizard/?p=search&view_by=custom&from=01%2F07%2F14&to=01%2F09%2F14&x=24&y=11 under Service Notice although on mine the text is somewhat garbled

[#5]

Hi ,
After reviewing your account it appears that your notification of the price increase was sent to you both by service notice/support ticket and email on the 18/07/14. The mail address we have on record is a mail.com address so a copy of this was sent here to confirm the changes as well.