[Reduced lot size?]

I started spread betting on IG last month. I have some investments in the US stock market. A total of 20 positions with half of the margin used.
I received this email from IG: 

Today is the last day you can enjoy our special introductory offer of reduced minimum lot and bet sizes.

Log in to your account now to benefit from the 75% reduction in minimum trade size, across all markets.

Does that mean they are going to increase my used margin by 4? In that case, I'm screwed and I will have a super margin call. 
I didn't even know I was under this promotion and I find it very unfair that I receive this email with only 24 hours notice, on a Saturday morning, with the markets closed and no chance to do anything to adjust my portfolio.

[Spread betting currency conversion fee]

On 03/06/2020 at 14:35, Caseynotes said:

Hi, yes though you can have a separate USD account so you are not changing back and forward all the time.

Hi @Caseynotes, I have the same kind of situation of the user who started this thread. I'm in UK, GBP account, but trading the US stock market. I can't find any info about having a second USD account. Do I have to open a new account all over again? Thanks for the info.