Drop-Down Menu Width

I’m having a very strange problem. I have been able to set the width of all my fields in the form, except for the “drop-down menu” field. No matter what I try the multiple select input field extends the full width of the form.

This is the CS7 form code I have used:
[text* your-phone placeholder “Phone*”]
Best time to call: (hold down CTRL or SHIFT to select multiple times)
[select* callback-time id:callbacktime multiple “8am” “9am” “10am” “11am” “Midday” “1pm” “2pm” “3pm” “4pm” “5pm” “6pm” “7pm”]

This is the CS7 custom CSS I am using to try and control the width, but the width command is being ignored:

.wpcf7 input[type=”text”],
.wpcf7 input[type=”email”],
.wpcf7-form textarea
{
background-color: #eceff4;
color: #000;
width: 55%;
border: 2px solid #323636;
}
/* Select field formatting */
#callbacktime
{
background: #eceff4;
width: 55%;
border: 2px solid #323636;
color: #4F4F4F;
}

The only thing I can think of is that a width setting somewhere else is overriding the drop-down menu field width. Could it be this?

/* Set table background and border colors */
.wpcf7-form {
border:2px solid #636364;
width: 90%;
background:#ecf4f2;
padding:20px;
margin-bottom:30px;
border-radius:7px;
}

The page I need help with: [log in to see the link]