Yes, but there are certain guidelines. No refunds are available for memberships, so if you want to switch from All Access to VIP, for example, you can, but there will be no refund for the difference in subscription costs.
If you wish to upgrade your membership, from VIP to All Access for example, you will need to pay the difference ($60 in this case). You will also be responsible for any additional shipping costs for sending you back issues that are part of your subscription year, should that apply to your situation. You may also choose to forego the rest of your current subscription year and start anew when paying for an upgraded membership.