If you’re in this situation, you could try leaving a message on their voicemail that makes them curious enough to want to call back. Say you’ve got some information that you know will be of interest or of value to them. And make sure you have!
Whether you have a relevant article, or some great results one of your other clients is getting, you must have a good reason to get them to call you back. Avoid the ‘courtesy call’ or ‘just checking how things are going’ approach – that can be irritating to a busy prospect and won’t compel them to ring back.
Of course, if you can, it’s even better to prevent this situation from happening in the first place. Don’t let a meeting or phone call end with a vague "I’ll give you a call at the end of the week, we should have a decision by then....” Pin them down to a specific day and time for the next contact.
Acknowledge that they’re busy “I know how full your diary is, let’s put a time down now, so we don’t end up playing telephone tag. Will 11 o’clock on Friday be OK for you?” And if, when you make the call, the decision hasn’t been made, repeat the process.
This approach isn't being pushy. It keeps you more in control of the situation and saves you precious time following up.

