To increase the size of a word in a middle of a normal font-size sentence:
Example:
<p class="call">To learn more about our services click here or Call Jack</p>
To enlarge the words Call Jack simply use this line of code in the paragraph:
<p class="call">To learn more about our services click here or <span class='bigger'>Call Jack</span></p>
Then paste the following CSS in your customizer:
.bigger { font-size:200%; }
All done!
– Jack