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