How to create option or combo box within cell?

I have attached my sample excel here for your convenience, please open it before you read the following so that you know what I mean, thank you in advance.

I have three sheets:Lead, Agent, Ref

Lead is the one I am focus on:

There are 10+ fields in Lead, some fields will link to Agent or Ref, for example, I want to give user the ability (when they fill in the form) to fill the Contact Type field with a combo box filled with the values from sheet Ref:
Phone
Cell
QQ
Email
WeChat
Address
Position

User will need to select from the list first, and then type in the Contact field the real content: if user selects Cell, then a cell number will be typed in field Contact.

for field Adviser I want combo box filled with the values from sheet Agent, similar as Contact but no need to have an extra field - but should auto generates the combo box for user to select from.

Is this possible? it seems to be a small database but my boss wants this be done in excel because she like simplicity.

Thank you very much in advance.